Iain Duncan Smith's official credit card has been suspended after the Work and Pensions Secretary ran up £1,000 in expenses debts, it has emerged, as he announced plans to ditch Labour's Child Poverty Act.

The former Tory leader was among a dozen MPs subject to action by the Commons watchdog after failing to show spending was valid, according to a Freedom of Information request.

The revelation overshadowed an announcement by Mr Duncan Smith to make it incumbent on governments to eradicate the problem of child poverty by 2020.

He said new laws will instead require UK ministers to report regularly on measures affecting a child's life chances.

Mr Duncan-Smith told MPs he was scrapping the official measures and targets used in the 2010 Act, which defines a child as being in poverty if it is in a household with less than 60 per cent of the national median average income.

He added it was deeply flawed because it meant tha tchild poverty was dependent on unrelated factors which had no effect on real lives, such as an economic slump or hike in state pensions.

Labour said the move represented the 'death knell of compassionate conservatism,' with his acting shadow spokesman, Stephen Timms, adding:" Their manifesto said they would reduce child poverty, insted they have decided to change the definition."

But Mr Duncan Smith insisted that it was an 'absolute priority' and that he had been consistent that not enough was being done to tackle the symptoms, without also tackling the underlying causes.

The Child Poverty Action Group said the Government was "turning its back on poor children" ahead of further welfare cuts expected in the Budget.

Meanwhile, Mr Duncan Smith's card was blocked by the The Independent Parliamentary Standards Authority (Ipsa). It issues MPs with credit cards for to pay for items such as travel and accommodation.

The politicians then have to prove the spending was genuine by the end of the month, or they build up debts to the watchdog. outstanding sums.

The debts were then recouped by not paying out valid claims filed by the politicians.

Mr Duncan Smith does not currently have any debt.

Former Labour MP Eric Joyce had his card blocked when he owed £12,919.61, and later had his salary docked. Others named included Rachel Reeves and Simon Hughes. All the debts have since been settled.