The proposed manifesto pledge, worth at least £3 billion, would mean that women would be entitled to full state pensions regardless of how many years they had worked.
At present women do not qualify for a state pension if they have not been in full-time work for at least a decade. They would be entitled to an annual payout of £4,139 under the plans.
Labour strategists believe the scheme could be crucial policy in key marginal constituencies of middle England, where middle-class women tend to fall foul of the system.
It is the latest policy from the government aimed at rewarding mothers who stay at home to bring up children — increasingly important as Britain’s population is forecast to decline.
However, the party will face accusations that it is trying to “buy” one of the most important groups of floating voters.
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The plan, heavily pushed by Alan Johnson, the work and pensions secretary, is facing opposition from Gordon Brown, the chancellor, who fears that it will undermine his attempts to reform the pensions system aimed at helping the poorest.
One cabinet minister said: “This plan is high on the agenda as there is a sense of real grievance that women who give up work to look after children may get nothing in retirement.
“But there are practical issues to resolve with the Treasury so it’s not yet a done deal.”
The chancellor fears that it will commit the government to a spending pledge that will have to be funded with savings made elsewhere in the benefits system.
A Downing Street source said: “The state pension system needs to be urgently reformed as women get a truly appalling deal.
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“The Treasury has long considered pensions to be part of their remit and have tried to block the plan but we are confident it will be in the manifesto. Downing Street has got plugged into pensions policy and realised it needs reform.”
At the moment the full basic state pension of £79.60 a week can be collected only by those with at least 39 years of full-time work and making National Insurance contributions. As a result of taking time off to care for children, just 14% of women qualify for a full pension.
The Downing Street source said: “Women can end up with no pension if they work full time for less than 10 years and devote their lives to raising children. It is a real injustice.”
Although poorer women have their pension entitlement increased with means-tested benefits, middle-class women usually lose out. Married women can claim about 60% of the basic state pension if their husbands have worked the required time. But they still face a shortfall worth more than £30,000 in retirement.
Johnson described the situation as a “national scandal” and is prepared to unveil his proposals for reform next month.
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The manifesto is likely to include a pledge that “women will receive a fairer deal on the basic state pension”.
The exact working and cost of the scheme are still being calculated but the state pension is expected to be based on the number of years a person is resident in Britain rather than the amount of time in full employment. The new system is expected to be introduced in 2010.
Mervyn Kohler, head of public affairs at Help the Aged, said that the charity would welcome the change. “We believe this is a welcome move forward to ensure women have a decent retirement,” he said.
“However, we still want the basic state pension to rise to at least £100 a week to lift pensioners out of poverty.”
Women are more likely to swing elections than men because they tend to switch parties more often. The so-called grey vote is also crucial as the over-55s will soon form the majority of the electorate.