In a key policy U-turn, the Tory leader admitted that the former prime minister John Major was wrong to cut the married couple's tax allowance, but claimed that Labour had worsened the situation by ignoring taxation altogether.
Speaking to the Conservative Christian Fellowship, Mr Hague also softened his party's traditional castigation of single mothers, yet insisted that "families need fathers" and that two parents were better than one.
He said that lone parents should be "respected" for their hard work in bringing up their children and that broken families were a fact of life for both the church and politicians. In a coded reference to the party's new tolerance of homosexuality, he also stated that those who led lives "very different from a traditional family pattern" should be free to do so.
Tax policy to aid and promote the family would now form a big part of the Tories' manifesto for the next general election, he revealed.
To combat the Government's stance on taxation, Mr Hague announced that his deputy leader, Peter Lilley, would head a new party task force on the family to tailor every area of policy to encourage marriage.
He claimed that the Chancellor, Gordon Brown, planned to abolish the married couple's tax allowance altogether and, as a result, end years of recognition of marriage within the fiscal system. Such a move would be "utterly wrong" as the state should not remain "neutral" about marriage and should instead promote it, he said.
Mr Hague said that it was baffling that the ministerial committee on family policy of Jack Straw, the Home Secretary, was expressly forbidden to consider how the tax system might be used.
In his most explicit comments to date on family policy, Mr Hague said that one of the consolations of opposition was that the Tories were now "free to think" about such issues.
"Looking back, I believe that we were right to introduce independent taxation for men and women, but that we made a mistake in not coupling this with a system of transferable tax allowances between husbands and wives. With hindsight, too, we were wrong to make such significant cuts to the married couple's tax allowance without putting anything else in its place."
In a significant shift from his party's opposition to single mothers and gay couples, Mr Hague said that he would not condemn anyone who chose an alternative lifestyle. "In a free society, that is their choice, and tolerance is one of the hallmarks of a mature and decent society," he said.
However, it was incontrovertible that two parents were better than one and that children were hurt by divorce. "Families need both fathers and mothers... Government figures show how divorce and single parenthood have added to welfare dependency," he said.
"It is not for any politician to berate or condemn. The Conservative Party is not against single parents; it is strongly and unreservedly for the institution of marriage."Reuse content