The government has been urged to bring forward proposals to introduce a transferable tax allowance as a way of recognising marriage in the tax system.
Leading a Westminster Hall debate on 28 November 2012, Conservative MP Stewart Jackson questioned "what is so backwards-looking in a country with so much social breakdown about saying that committed relationships are a bad thing?"
While in opposition the Conservatives promised a transferable tax allowance, possibly worth £150 a year, to married couples. It would apply where one spouse stayed at home.
But Liberal Democrat leader and Deputy Prime Minister Nick Clegg has said the idea of tax breaks for married couples is wrong, and will not work.
Mr Jackson was supported by his Conservative colleague David Burrowes, who claimed that Mexico was the only other developed country that did not recognise marriage in the tax system.
However Labour's shadow treasury minister, Catherine McKinnell, said she was "not convinced" that the tax system was the best way of supporting marriage.
Since 1990, all individuals have been assessed for tax as separate persons, and in 1999 the then Labour government announced that the Married Couple's Allowance (MCA) would be withdrawn.
In 2007, the Centre for Social Justice published a report calling for tax breaks for married couples, saying the welfare system needed to be reformed to "strengthen the family".
Winding up the debate, Treasury Minister David Gauke said that the government was continuing to "find ways to support marriage and civil partnerships in the tax system".