Backbenchers in the  British Conservative party yesterday tried to push Prime Minsiter David Cameron into giving tax breaks to married couples.

At least ten MPs backed an amendment which would allow husbands and wives to share income tax allowances – a reform that would benefit the couples by up to nearly £1,500 per annum.

Their aim was to pressure the Mr Cameron into making good his longstanding pledge to promote marriage.

Earlier this year, influential think-tank the Centre for Social Justice, which was founded by former Tory leader and current Welfare and Pensions secretary Iain Duncan Smith, gave the Government low marks for how it had handled marriage.

It pointed out that the Government’s Budget, quite apart from not doing anything in the tax system to help married couples, had actually made life tougher for hundreds of thousands of families on a a single income.

Earlier this month, Mr Cameron repeated his promise to help marriage in his speech on feckless fathers, saying: ‘I want us to recognise marriage in the tax system so, as a country, we show we value commitment.’

A supporter of the amendment said: ‘David Cameron and other senior Conservatives repeatedly expressed their commitment to recognising marriage in the tax system during the last Parliament.

‘This was a key policy response to the challenge of social breakdown – the Broken Britain phenomenon – and became an important manifesto pledge.

‘The commitment got into the Coalition agreement, but no action has yet been taken.’

Critics say the decline of marriage is a central factor behind rising social disruption and family break-up. Work and Pensions Secretary Iain Duncan Smith has warned that this costs the country £100billion a year.

The rebel backbenchers yesterday put down an amendment to the Finance Bill which is setting Chancellor George Osborne’s March Budget into law.

A transferable income tax allowance would mean that a working husband could take over the tax-free allowance of a wife who stayed at home to bring up children, or vice versa.

It would be worth up to £1,495 to a one-earner couple. The backbench initiative, which is unlikely to become law, was attacked by Labour.

During Labour’s years in power the last tax break for husbands and wives, married couples allowance, was removed, and the importance of marriage eroded to the point where officials were told to remove the word from public documents.

Labour Treasury spokesman David Hanson said: ‘It is astonishing that at a time when millions of families and pensioners are being hit hard by deep spending cuts and tax rises, the first priority of David Cameron’s restless Tory backbenchers is unfair tax cuts only for a few.

‘And the proposed multi-billion pound marriage tax break would penalise those who are separated, widowed or divorced – many of whom are already being hit hard by cuts to tax credits and childcare support.’

Mr Cameron is thought to be holding back on a firm promise of tax breaks for married couples on the grounds that the country cannot afford it.

Calculations by the Centre for Social Justice think-tank suggest it would cost £600million to give a transferable tax allowance to married parents of young children, and £3.2billion to extend it to all married couples.

In the run-up to last year’s election, Mr Cameron said: ‘I just think as a society, saying that marriage is a good thing and celebrating it and encouraging it, including through the tax system, is something that most societies do in Europe. It’s very sensible for us to do as well.’

The idea also appeared in the the Coalition agreement which says that a transferable allowance for married couples will be introduced.

But it gives no details or timetables, and it allows the Lib Dems to abstain on any vote to bring it in.

The Lib Dems have threatened to oppose the measure, and have successfully insisted that their own policy of raising the personal allowance to £10,000 must take priority.

“This is about putting down a marker, making sure that the policy isn’t forgotten,” said a supporter of the measure. Senior Conservatives are keen to push ahead with the marriage tax break, and Treasury officials are understood to be studying ways to implement the policy.

But one Tory minister said it would help to ““keep the issue on the agenda” within the Coalition.