David Cameron's government has ruled out cuts to child benefit to help ministers slash £12 billion from the welfare bill.

The move follows reports that Iain Duncan Smith, the Work and Pensions Secretary, has ordered officials to consider limiting payments to just two or three children per family.

Civil servants were also asked to look at reducing the amount of money that parents receive for their first child.

No 10 said that the Prime Minister had pledged that there would be no cuts to child benefit.

A Downing Street spokesman added: "The PM was very clear during the election and his views haven't changed... that there should be no cuts to child benefits."

Asked if he would keep child benefit in its current form for the next five years the Tory leader said at the time: "Correct, correct, I said that last night and happy to say it again."

Ministers are under pressure to find billions of pounds worth of savings after the Conservatives won the General Election with an outright majority last month.

In the run up to the vote the Tories pledged to cuts £12 billion from welfare if elected.

But the party would not say during the campaign where the axe would fall.

Mr Duncan Smith admitted that the Conservatives had not yet "done the work" to see where the savings could be found.

The the independent Institute for Fiscal Studies think tank calculates that limiting child benefit could save £2.5bn a year.

The government has already announced plans to freeze working-age benefits for two years.

Labour called on the government to "come clean" with the public about further cuts.

Stephen Timms, Labour's shadow work and pensions minister, said: "In the election campaign David Cameron promised that child benefit would not be cut in this parliament.

"It is increasingly clear that millions of working families are in the Government's firing line.

"It's time for David Cameron to rule out reducing the real value of child benefit or child tax credits and cutting the number of families who are eligible in this parliament.

"The Tories should come clean with the public."

There are two child benefit rates.

Parents receive £20.70 for their eldest or only child and £13.70 for every child after that.