Support for families is being pledged in the run up to the election
Labour and the Conservatives have been setting out their plans to support families - expected to be a key election battleground.
Labour says it will change the law so that if parents split up, grandparents will not have to go to court to apply for contact with grandchildren.
They also say they will give fathers more support in bringing up children.
The Conservatives have accused Labour of stealing their policies - especially on grandparents' rights.
Ministers say employers and health and children's services in England all need to recognise the role fathers have in caring for children.
Fathers will be given more information before a child's birth to encourage them to be responsible parents.
Labour's Families and Relationship Green Paper - being released today - sets out a wide range of measures designed to support "all families".
Under Labour's plans, separating couples will be strongly encouraged to seek mediation rather than going to the family courts to settle problems.
On the BBC's Today programme, Children's Secretary Ed Balls clashed with Conservative Families Spokesman David Willetts over the issue of giving tax breaks to married couples.
Mr Balls said he supported marriage, but did not believe it should be reflected in the tax system.
"The evidence shows that if you are married, children do better, although once you adjust for the fact that people who are married tend to marry older, be better educated and have higher incomes, once you adjust for these things, you find that it is not the legal form, it is the strength and stability of the relationship which is the most important thing," he said.
"What I am not going to say is that if you are a widow or if you are a lone parent because your husband threw you out in an abusive relationship, you should be disadvantaged."
Mr Willetts said the Conservatives were committed to looking at the most effective way of "helping marriage through the tax system", although this was not something which would happen immediately if his party came to power.
He said: "You could have transferable allowances. You could have married couple allowances. There is a range of ideas and that is what we are looking at.
"This is something we are committed to doing in the lifetime of the next Parliament.
"It is not something we are likely to be able to do in the first budget.
"That means, if there were a Conservative government, it is something we would have the time to consider what was the most effective way, given the state of the public finances, for helping marriage through the tax system."
But Mr Balls suggested that the Conservatives would opt for a transferable income tax allowance for married couples which would cost £4.9 billion and benefit wealthier families while penalising widows, divorcees and couples where both partners work.
Mr Willetts said any attempt to use the tax system to support relationships outside marriage would be "incredibly complicated and intrusive".
He added: "We are talking about a widespread aspiration. If you look at the evidence, most people still aspire to get married.
"It is a very good environment for bringing up kids and it is absolutely right that a government, when choosing how it reduces the tax burden, should reduce the tax burden on this incredibly valuable and important social institution."
Later, Mr Willetts launched the family section of the Conservative Party's Draft Manifesto.
The party says it would make Britain more "family-friendly" by reforming the tax and benefits system, by "taking a new approach to early intervention and by "helping families to balance their lives".
Mr Willetts said: "We can't go on ignoring the importance of strong families.
"They provide the stability, warmth and love we need to flourish as human beings, and the relationships they foster are the bedrock on which society is built."
The draft manifesto he said outlined "a comprehensive approach to encourage stability and tackle social breakdown - a new system of flexible parental leave which lets parents share maternity leave, more health visitors to support new parents, and encouraging commitment by recognising marriage in the tax system".
Liberal Democrat families spokesman David Laws told the Today programme the key thing was stability - and it would be better to direct funds at helping children through the education system.
He said:"We are deluding ourselves as a nation if we think that some sort of small tax break is really going to make a fundamental difference to parenting or marriage.
"The key thing is whether there is stability and whether there is love and that can often be highly associated with marriage but it is not exclusively associated with marriage."
"The policies Ed Balls is announcing - the Dads' Guide and the websites - will make very little difference. I would put all of this money into the education system.
"Focusing that money on those children - giving them skills, aspirations, as much stability as we can and the life skills they need - will do far, far more to promote responsible citizens and good, stable families."
Government plans to involve fathers more in child-rearing include leaflets targeted at them, which will be distributed from next month.
Research suggests fathers who are involved with the birth of a child are more likely to stay involved in the child's first three years of life.
And longer term involvement leads to children having higher self-esteem, educational achievement and fewer behavioural problems, research says.
Recent studies suggest more and more fathers are sharing and even taking over responsibility for childcare.
The booklet for new fathers is being drawn up to give tailored advice and tips to fathers ahead of a new birth.
Written with the Fatherhood Institute, officials say it will be a "myth-busting guide" about how fathers can be just as good hands-on carers as mothers.
It will also offer advice about legal issues like registering the birth, health issues for both parents, communicating with the baby and keeping him or her safe, providing financially and maintaining a good relationship with the mother.
A spokesman for Families Need Fathers said it had been lobbying to make proper mediation compulsory before attending court, and that it was encouraged that the government would now consult on this.