So Mr Cameron, is it right that I will pay more tax because I haven't found Mr Right?

David Cameron was accused of "discrimination" and "perpetuating stereotypes" by a group of single parents yesterday as he was forced to defend his party's policy of handing tax breaks to married couples.

In a speech to members of the single parent charity Gingerbread – which was not advertised to the media by his aides who feared the Tory leader would face a rough ride – Mr Cameron denied being "at war" with single parents.

However, he insisted that government should not remain "neutral" on the issue of family, and had to send "long-term signals about commitment".

He said: "My view is that there is an importance in trying to say that commitment and relationships and marriage are good institutions. They are good things. We shouldn't be completely neutral about them as a society.

"I think the tax system and the benefits system, as well as helping people in the here and now as it should, also does need to think about what other long-term signals we are sending out as a society.

"We should be sending long-term signals that are about commitment and the things that encourage commitment. It doesn't disadvantage other people, it's just saying that this is a good institution that society should recognise in such a way."

Mr Cameron said single parents would not be "on their own" under a Conservative government but that he believed the state should encourage people to stay in relationships wherever possible. "That's why my party will back marriage in the tax system and end the couple penalty that pays people to live apart rather than together," he said. "But – and let me be very clear about this – the flip side of this coin isn't disapproval of those who don't stay together. I get the real world. Sometimes, however hard you try, a relationship is not going to work."

One single mother demanded of Mr Cameron: "You talk about tax, and that you are looking at providing tax cuts for married couples. Do you not think that is discrimination against someone who pays their tax bill every month, and someone who is going to find that my friend down the road who has managed to find 'Mr Right' gets away with paying less tax than I do, just because I am raising my children by myself?" She continued: "Also, don't you think that's perpetuating the stereotype that actually a married couple is better than a single family?"

Applause broke out when another woman asked how the Conservatives intended to fight false stereotypes about single-parent families. Mr Cameron replied: "I think we all have a role in trying to make sure that we portray things in a more reasonable way and a less black-and-white way."

One mother who attended the meeting told The Independent she felt it had been a success, but that single parents were unlikely to vote for the Tories unless they changed their policies. "Many people felt it was quite a coup to have David Cameron sitting there, because he was somebody high profile who was at last taking us seriously. Now, work needs to be done about shaping their policies to take on board our concerns – at the moment I don't think the policies are there." Gingerbread chief executive Fiona Weir added: "While we welcome his strong message about stigmatising, we would like to see them reflect that through policies. He risks making single parents feel like second-class families."

Stephen Timms, Financial Secretary to the Treasury, accused Mr Cameron of being in an "utter mess" over the issue of tax breaks for married couples. "He says he's deadly serious about marriage and intends to spend billions on a tax giveaway to wealthier married couples. Then he tries to deny to an organisation of single mums that he intends in any way to discriminate against them," he said.

Family values: The Tory tax proposals

*The Conservatives plan to support marriage through the tax system, by allowing married couples to combine their tax-free allowances of £6,475 and increase their incomes. The policy is designed to reinforce the importance of strong family units and would help couples where one parent stays at home with young children.

*Reform of the benefits system, which David Cameron claims "pays people to live apart rather than together", is also proposed.

Sasha Corcoran: He talked well. It's a shame he didn't listen

Eyewitness: When Mr Cameron arrived with his supporters, he seemed to be nervously looking around the room. You could see that he came equipped to say what he thought we wanted to hear – that became very obvious, because he was effectively reading from a script. It was about giving a speech that was going to tick some boxes. It was a very clever speech, and it did tick a few boxes, but it was definitely looking at the wider issues of families and children rather than really homing in on lone parent issues.

He was very professional and when it came to the questions he wasn't stumbling to find the answers – but I'm not sure he really listened to the questions. He did the typical politician's thing where he heard the question but then went off on a tangent in order to answer it. Today was about trying to win over some lone parents and getting their votes but why would I vote for somebody who's going to make me worse off than somebody who's married, just because they're deemed to be 'better?'

Is the Conservative Party going to set up a sort of dating club for all us single mums to find husbands, so we can get a tax rebate?

Sasha Corcoran, 38, watched David Cameron's speech yesterday. She became a parent at the age of 17 and has two children.