The motion says Mr Brown is wrong to argue that the scheme mainly helps high-earners, insisting it is families just above the threshold for means-tested benefits that benefit the most.

And it “calls on the government to consider the serious implications of the proposal for worsening the gender pay gap and reducing opportunities and incentives for two parents to work”.

Some MPs fear the issue could become as politically damaging to Labour as Mr Brown’s notorious decision to axe the 10p tax rate, which triggered a huge public backlash.

Working women are a particularly important voter group for Labour, which has ploughed huge resources into benefits such as increased maternity leave and pay.

Among senior Labour figures angry at the scrapping of vouchers are former Health Secretary Patricia Hewitt and Caroline Flint, the former Europe minister.

Both parents can use the vouchers, potentially saving couples £2,390 a year. Each higher rate taxpayer can save £1,195 and a basic rate taxpayer £962.

However, a No 10 source insisted: “This was not designed as a benefit for rich people. It is not being as well targeted as it should. We believe it is right to redirect the money at nursery places for two-year-olds.”