The government's flagship welfare reform policy is "collapsing into chaos", shadow work and pensions secretary Liam Byrne has said.
Under current plans, income-related jobseeker's allowance, housing benefit, child tax credit, working tax credit, income support and income-related employment support allowance are all being merged into one payment: the universal credit.
At work and pensions questions in the Commons on 25 June 2012, Mr Byrne alleged that the introduction of the universal credit was running late and over budget, and the prime minister's recent speech on welfare reform was designed to deflect attention from this.
He explained: "The minister for unemployment said to the House that all out-of-work benefits were supposed to be treated as universal benefit applications from October 2013. The DWP [Department for Work and Pensions] newsletter from last month says that now won't happen until mid-2014, nine months late."
He said the project had been expected to cost £2bn, but parliamentary answers now suggest that "it is £100m over budget".
"Universal benefit is not on time, and it's not on budget, and the secretary of state doesn't know what's going on in his own department," Mr Byrne said.
"So is it any surprise that the prime minister had to announce another revolution in welfare reform this morning, because the last one appears to be collapsing into chaos?"
Work and Pensions Secretary Iain Duncan Smith flatly rejected the accusation.
"It's so typical of the right honourable gentleman," Mr Duncan Smith said. "He knows that universal credit is a programme that will be introduced over four years."
The opposition spokesman needed to "check his figures again", he added.
"There's something really rather pathetic about the way he pauses on little figures and seems to think that that spells something at all," the secretary of state concluded.