Mr Field, whose analysis is based on the annual report of the CSA and written parliamentary replies to MPs, said that the cost of agency continued to increase. “It now costs taxpayers 54p for each pound of maintenance the agency collects.”

He added that the reforms introduced by Labour in 2003 — which have cost the taxpayer £456 million for the new IT system alone — have added to the agency’s “general chaos and declining performance, and made an intolerably poor service even worse”.

He told the Prime Minister that two years on, it was now clear that these reforms, far from improving the CSA performance, “have added to the general level of chaos we inherited”. Mr Field said: “Indeed, in practically all respects the CSA now performs worse than it did a year after the 1997 election.”

Sir Malcolm Rifkind, Shadow Work and Pensions Secretary, said: “Frank Field was asked by the Prime Minister to think the unthinkable on welfare reform. He did, and Mr Blair ignored him. These new revelations are a damning indictment of the Government’s welfare reforms by one of its own former ministers charged with welfare reform.

“The CSA is in chaos with some cases being handled on the old system and some on the new system with little sign of improvements in performance on the horizon.

“The Government must get a grip on the continuing fiasco that is confusing families and penalising families that need a system that actually works.”()

A GRAND PLAN TO MAKE PARENTS PAY