All married couples would qualify for a £20-a-week tax break under plans being considered by the Conservatives.
Married couples where one person does not work should get a £20-a-week tax break, a Tory policy group suggests.
It is one of 200 proposals put forward by a Tory policy group headed by former party leader Iain Duncan Smith.
Former party leader Iain Duncan Smith's policy group also wants higher benefits of £32-a-week for married parents to bring them into line with lone parents.
Others include higher benefit payments of £32-a-week for married parents to bring them into line with lone parents.
Mr Duncan Smith said the balance had to be "re-set" in favour of marriage.
Labour believes the Tory proposals would "discriminate" against the children of single parents and those of unmarried couples.
But the government said the Tory proposals would "discriminate" against the children of single parents and those of unmarried couples.
The Conservatives are expected to adopt some ideas - but reject others - outlined by the policy group, which says the cost of more than £6bn could be met by tougher welfare rules.
Binge drinking
BBC political editor Nick Robinson said the most controversial proposals around marriage amounted to "tough love" for lone parents, but greater help for those who are married.
The Conservatives are expected to adopt some of the ideas outlined by the policy group, which says the cost of more than £6bn could be met by tougher welfare rules.
'Big risk'
It's not going to be a golden bullet Iain Duncan Smith
He said if David Cameron chose to back the policies, it would be one of the biggest risks he has taken since becoming party leader.
The transferable tax allowance, worth around £20-a-week, would be aimed at making it easier for one parent to stay at home to look after children or elderly relatives.
The transferable tax allowance, worth around £20-a-week, would be open to all married couples - aimed at making it easier for one parent to remain at home to look after children or elderly relatives.
We need a big cultural change in favour of fatherhood, in favour of parenting, in favour of marriage David Cameron
If applied to all married couples, it would cost £3.2bn a year.
If applied to all married couples, it would cost £3.2bn a year.
Further proposals put forward by the group include:
Further proposals among the 200 put forward by the group include:
Raising the tax on alcohol to tackle binge drinking
Raising tax on alcohol to tackle binge drinking
State schools which are judged to be "failing" to be taken over by parents and charities, while pupils in disadvantaged schools should get £500 for extra tuition - academic, musical or sporting
State schools judged as "failing" to be taken over by parents and charities, with pupils in disadvantaged schools getting £500 for extra tuition - academic, musical or sporting
Reclassifying cannabis - which was downgraded to a class C drug - back to class B again
Reclassifying cannabis - which was downgraded to a class C drug - back to class B
A greater role for credit unions offering low-interest loans to low-income families to help protect them from loan sharks
A greater role for credit unions offering low-interest loans to low-income families to help protect them from loan sharks
Dr Samantha Callan, of the Centre for Social Justice, who worked on the Conservative proposals, said: "What we are trying to do is support an institution that does, on average, deliver better outcomes for children and adults.
Asked about the tax-break plan, Mr Duncan Smith told BBC Radio 4's Today programme: "It's not going to be a golden bullet that says somehow this will persuade everybody to come together and stay together.
"And it's not just about giving people money. It's actually saying... why should you lose your tax allowance because you are not doing something that's outside the home?"
"It's part of a balanced package of benefit changes and taxes that will actually say to people: look, it's not to penalise you any more."
Mr Duncan Smith said the current system "penalised people who are wanting to stay together" and that he was "trying to re-set the balance".
'Wrong to preach'
'Wrong to preach'
But Cabinet Office Minister Ed Miliband told BBC Radio 4's Today programme the government would not "discriminate against some children" in its tax policy.
But Cabinet Office Minister Ed Miliband said the government would not "discriminate against some children" in its tax policy.
He also said: "I don't think it's right for politicians to come on and preach."
He also said: "I don't think it's right for politicians to come on and preach."
Camila Batmanghelidjh, founder of the Kids Company charity, said she did not approve of the Conservatives' proposals.
Liberal Democrat work and pensions spokesman David Laws said: "A lot of the [Conservative] solutions are a bit naive - to think that we can simply tweak the taxation system and bring about a big change in people's behaviour."
She said: "I don't see how it is going to help people or affect in any way people staying married or people getting married.
Mr Duncan Smith's policy group warned last year that an underclass was being "left behind".
"And I think it is unfair when there are people living happily together to not give them the same tax incentive."
The Conservatives have said mending Britain's "broken society" should be a top priority - rather than the traditional emphasis on tax and crime.
The final findings of Mr Duncan Smith's Breakdown Britain report will be published on Tuesday.
Party leader David Cameron has called for more voluntary and community action to deal with social breakdown.
The policy group warned last year that an underclass was being "left behind" by the rest of society.
The Conservatives have concluded that mending what they call Britain's "broken society" should be a top priority - rather than the traditional emphasis on tax and crime.
They say they want to put an end to the economic cost of "social malaise" - debt and addiction, welfare dependency, family breakdown and education failure.
Party leader David Cameron has said he wants to encourage more voluntary and community action to deal with social breakdown.
On Sunday he told the BBC there was something "deeply wrong" with society which needed "long-term generational change".
He is expected to welcome the proposals but stop short of announcing any specific policy.
