Labour has warned that millions of childless and unmarried people would face higher taxes under a Tory government under plans floated by David Cameron.
The Tory leader, who has promised to reward marriage through the tax system, pledged that "every pound" of new green taxes to combat climate change would be spent on cutting "family taxes". He said: "I think people will have faith in green taxes if we say every pound on a green tax will come off a family tax."
Labour ministers seized on his remarks, claiming that people not in traditional families would miss out on the compensatory tax cuts on income while paying the new environmental taxes. Mr Camer-on's commitment to cutting taxes for married couples with children had come under fire during a Newsnight interview earlier in the week, when the journalist Stephanie Flanders challenged the Tory leader on the issue: "I'm not married, I have a small child," said Ms Flanders. "Are you saying the Conservative Party would like me to be married?"
After a moment's pause, Mr Cameron said that he was not interested in running other people's lives but added: "I am unashamedly pro-family. For me it comes absolutely first."
Labour has painted Mr Cameron's comments as the latest evidence of a drift to the traditional Tory right.
Andy Burnham, the Chief Secretary to the Treasury, said: "Increased taxes on motoring, holidays and household fuel bills will hit every person hard. It is the latest evidence of David Cameron's massive lurch to the right."
But George Osborne, the shadow Chancellor, replied: "We will shift taxation from the income that people earn on to pollution. Unlike Labour ... any increase in green taxes we offer the public will be matched by tax reductions elsewhere. That is the way to deal honestly with the public and responsibly with the environment."
The Tories denied Mr Cameron was pandering to the party's "core vote" after he warned on Wednesday that the level of immigration was "too high". Damian Green, the Tory spokesman on immigration, said: "In no way is this a move back to a core vote strategy. [David Cameron] was asked a straight question about immigration policy and he gave a straight answer."
Mr Green insisted that "community cohesion" was at risk because an influx of immigrants put pressure on public services.
But Tim Montgomerie, editor of the ConservativeHome.com website, hailed Mr Cameron's remarks as an important shift. He said there had been "various overtures" on the four "core vote issues" for Tory members – Europe, tax, crime and immigration. He added: "For a lot of us grassroots who have wanted to see this shift, it is beginning to happen."