The Conservative Party has come under attack from Labour and the Liberal Democrats for their plans to introduce tax breaks for married couples.
Commenting on the Tories' marriage tax proposals from Iain Duncan Smith's think tank, The Centre for Social Justice, Lib Dem leader Nick Clegg said on BBC One's Andrew Marr show: "David Cameron is plain wrong, totally wrong, to say that we, the country, should spend billions of pounds providing a tax bribe for people simply to hold up a marriage certificate.
"It is immensely unfair. What does it mean for the poor woman who has been left by some philandering husband who goes on to another marriage and gets the tax break and she doesn't?"
Writing in the Mail on Sunday, Conservative leader David Cameron set out his party's plans to give married couples a tax break. "A stable home is the best start a child can get. That's why we'll back commitment by recognising marriage in the tax system - and we'll also end the couple penalty in the tax credits system which, unbelievably, encourages parents to live apart," Mr Cameron wrote. However the Conservatives are yet to provide any detail of their plans.
Following mounting criticism today, Shadow foreign secretary William Hague defended the proposal, saying: "It has got to be right to support families and supporting marriage is part of that."
Ed Balls, the Schools Secretary, branded the proposed tax reforms as 'social engineering'. In an interview published in the Sunday Telegraph , Mr Balls said: "The idea of trying to socially-engineer family life through a tax policy which is designed to say that some types of families are first class, and other types of families are second class and should be financially disadvantaged, is hugely expensive and unfair.
"It could stigmatise children and I don't think that's right. I don't think children should be told they are second-class kids because of things which have happened through no fault of their own or unavoidable reasons," he added.
Family policy is set to be a major general-election issue as the three main political parties remain divided over their approach.