Taxes and benefits must be transformed to strengthen families and cut the "social breakdown" which costs £102bn a year, a Tory policy group says.
Mr Duncan Smith said the balance should be 're-set' to help marriage
Former party leader Iain Duncan Smith's report calls for the "biggest shake-up of the welfare system" since the 1940s.
It backs tax breaks for some married couples, trebling child benefit for the first three years and getting more single parents off benefits earlier.
But Labour said the proposals would "discriminate" against some families.
Mr Duncan Smith's policy group was established by Conservative leader David Cameron to advise on policy options - its recommendations are not binding on the party.
It says social breakdown results in costs to the UK of £102bn a year - with family breakdown taking up £24bn, crime £60bn and educational under-achievement £18bn.
The transferable married couples 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.
If applied to all married couples, it would cost £3.2bn a year, and is one of 190 policy recommendations in the near-700 page report.
Key proposals include:
- Allowing parents to "front load" child benefit, getting up to £2,800 a year up to the age of three and less when the child is older
- Lone parents expected to work 16 hours a week when youngest child reaches five and 30 hours a week when youngest child reaches 11
- Raising tax on alcohol to tackle binge drinking
- 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
- A greater role for credit unions offering low-interest loans to low-income families to help protect them from loan sharks
- Raising the gambling age limit from 16 to 18
Mr Duncan Smith said the tax break plan was not a "golden bullet" to preserve marriage, or about "finger-wagging or moralising".
But, he said, the current system "penalised people who are wanting to stay together" and that he was "trying to re-set the balance".
"The Government seems to have taken the view that they don't much like marriage," he said.
"Almost alone in Europe we have no recognition of marriage in the tax and benefits system."
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."
Liberal Democrat schools, families and children 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."