Claire Champkin with six-year-old Toby who has autism. Photograph: Graeme Robertson for the Guardian Graeme Robertson/Guardian

Jane McCready is used to her 10-year-old son being gawped at "as if he were a circus freak" but she will never be reconciled to it. "Children are one thing, they don't know any better. But these are adults. They look at Johnny and their mouths fall open and they just stare. And I think: didn't anyone ever tell them how rude that is?"

Johnny has severe autism and learning disabilities. "He looks like any other child, but he behaves oddly – for example, he might sit there banging two toys together – and he sometimes makes strange noises." Especially when he was younger, he might have a massive meltdown – at the supermarket checkout, for instance. "I'd feel 300 pairs of eyes on us – all watching us, all judging us for being disruptive and difficult," says Jane. Perhaps the worst day was when, at the swimming pool, another mother pulled her child away from Johnny "as though he had something catching".

This, she says, is what you are up against when you have a child with special needs: other people tend not to be very kind. Which is particularly awful "because you've already got so much on your plate as it is. The odds seem stacked against you, and if people just gave you a bit of space and support, it would go a long way. But the opposite is more often the case: you're struggling to start with, then people knock you down further. They make assumptions about you, they find you wanting, they treat your child as though he or she is dangerous or badly behaved. It's soul destroying. It's so bad, so hard to deal with, that I have friends with special needs kids who don't even take them out any more."

Jane, 49, who lives in south London, turned to Mumsnet to vent her feelings; and she was not the only parent in her situation to do so. Mumsnet members who didn't have children with special needs were shocked at their stories, and so too were the women who run Mumsnet. "We realised how incredibly hurtful some of the behaviour they were describing was, and realised we should do something," says co-founder Justine Roberts. "It's about letting judgmental feelings go and stopping all the tutting from the sidelines.

"The truth is that it's incredibly tough to have a child with a special need such as ADHD or autism. In many cases, it's a 24/7 job and to have to suffer the prejudices of others on top of that is just too much. There's a strong feeling on Mumsnet that how we look after our most vulnerable says a lot about our society and you don't get much more vulnerable than children with special needs. So we need to up our act a bit, as a society."

To that end, Mumsnet this weekend launches This is My Child, a campaign aimed at getting us all to think a bit more about the realities of life for families with children who have special needs and to check our behaviour accordingly.

"A little bit of help goes a long way," says Jane. "One time Johnny was melting down and this woman approached me. I thought she was going to complain – you get people who say things like, all he needs is a good slap. When she said 'What can I do to help, dear?' I could have hugged her. It must have taken some bravery for her to do it, but it made such a difference to me. I felt someone was on my side rather than the usual wall of hostility."

Claire Champkin, 40, who lives in Twickenham, Surrey, knows just how Jane feels. she says the biggest difficulty about life with six-year-old Toby is the negative attitudes of others. Her son has moderate-to-severe autism, and is largely non-verbal, but dealing with the realities of his condition pale next to dealing with the unkindness she encounters from strangers who decide for themselves that he is simply a badly behaved child with an inadequate mother. "One day we were in the park, and a father who was sitting on a bench pushed his glasses down to the end of his nose and sat there staring at Toby in evident disapproval. I felt like heading across to shout and swear at him, but you can't do that.

"What do people think gives them the right to behave that way? And the irony is, they think they're making a judgment on my child's bad behaviour."

Amanda Marlow, 43, who lives in Milton Keynes, says she has survived by growing a skin so thick she doubts anyone's disapproval could penetrate it. "Sometimes I think if I marched through the shopping centre with 'fuck off' written on my forehead, I couldn't be more obvious about it," she says.

She has four children, twins Elizabeth and James, 13, Oliver, seven, and Alex, six. Elizabeth has Treacher Collins syndrome (which causes craniofacial abnormalities); James has Asperger's syndrome and Alex has severe autism.

"What I'd like people to understand," she says, "is that these are my children. This is my life. It's not a bed of roses, but we try to make the best of every day. What would be nice is if people were kind and considerate once in a while, and gave us a bit of space. We're dealing with issues that most people haven't got a clue about, and it's intrusive when you get someone coming up to you and saying, he needs a clip round the ear when one of them has a tantrum."

If Amanda, Claire and Jane could ask the rest of us to do just one thing, it would be to stop staring. "It's fine to do a double take, but once you've taken in that our children have a disability, get on with what you're doing. It doesn't give you the right to gawp," says Claire.

Beyond staring, what angers Amanda is when strangers ask about Elizabeth. "They say, what's wrong with her? And I say, nothing's wrong with her. She's fine."

Claire agrees: it's not a tragedy, she says, that her child has a disability. "We don't need pity; we're a very happy family and we just want to get on with our lives. I hate people calling me 'special' or thinking I somehow have extra qualities that enable me to deal with all this. The truth is that when it happened to me, I thought I couldn't cope.

"But a very wise person said to me: 'You'll cope because you have to.' And that's what anyone would do. Calling us 'special' or alluding to our great qualities makes us different, sets us apart, and we don't want that at all."

What is also irksome to many parents is when other people take it on themselves to reassure them that all will be well. "I get that all the time," says Ellie Grant, from Wiltshire, whose three-year-old daughter Roberta has the chromosomal disorder Kabuki syndrome. "Roberta had hip dysplasia and, when she was in plaster, people would say: 'She'll be walking soon enough and you'll wish she wasn't.' That's so hurtful – the idea that when she does one day walk, I'll wish she couldn't."

The other thing they often say is how gorgeous and cute Roberta is, as if that is somehow incompatible with a disability. The people you value most are those who just treat you as they would any other family. I love it when people meet us and they try to engage with Roberta, just as they would any other child; that's so good. What I don't need is sympathy; I'm hugely proud of my little girl and all she's achieved. She and her baby brother are the centre of my world and the idea that people feel sorry for me is just so misplaced."

There are around 770,000 disabled children in the UK and, says Justine Roberts, their families deserve better. "A lot of it is about raising awareness about the reality of their situation, and busting some of the many myths. There's a myth that some disorders, such as autism and ADHD, are a fashionable excuse for bad behaviour and bad parenting. Wrong: these conditions are real and disabling and it is terrible that the parents and families of those with them are stigmatised.

"Another myth is that children with disabilities are given the help they need. In fact, Mumsnetters tell us time and again about how little help there is, how much they have to fight for everything they're given and how long it takes even to get their child's condition diagnosed."

Another myth, says Justine, is that language around disability doesn't matter. "You get a lot of people who use words like 'retard' and 'mong' and for some reason that's tolerated, while language that's racist or sexist or homophobic definitely wouldn't be. We've learned how hurtful it is to families where there are disabilities, and now we clamp down on it on the site – and we'd like others to do the same. It really is important. It really does make a difference."

What you can do

• You can't always tell when someone has a disability. Respond kindly, not judgmentally.

• Don't make assumptions about a child's potential based on a label. People with disabilities have a range of capabilities, just like anyone else.

• If people seem to be struggling, ask: "How can I help?" or "What do you need?"

• Saying "at least it's not cancer" is not helpful.

• If there is a child with a disability in your child's class, invite him or her over to a playdate, or include him or her on the birthday party list. Too many parents of children with special needs kids say their kids miss out on peer activities.

• And one last time: don't stare. Really. Just don't.

Source: mumsnet.com/campaigns/this-is-my-child

More information at mumsnet.com/campaigns/this-is-my-child