A spending watchdog has hit out at the failure of Whitehall departments to join a major anti-fraud initiative which has uncovered £275 million of scams, overpayment and errors in the past two years.
Audit Commission chairman Michael O'Higgins called on the head of the civil service to force them to participate - claiming there was "no defensible case" for their absence.
His appeal - in a letter to Sir Bob Kerslake expressing serious frustration - came as the body released the latest results of the National Fraud Initiative (NFI).
It continually compares data held by 1,300 public and private-sector organisations from across the UK, including the commission's equivalents in Scotland, Wales and Northern Ireland.
Figures for the last two years show pensions (£98 million), council tax discount for single occupiers (£50 million) and housing benefit (£31 million) are the biggest problem areas.
It also rooted out 164 illegal foreign workers and 321 fake council house applications, and led to the cancellation of tens of thousands of wrongly-held disabled parking badges and travel passes.
The commission said it resulted in 731 prosecutions - 636 for housing benefit fraud.
Mr O'Higgins said the scheme was "well on its way to returning a landmark £1 billion to the public purse, money that would otherwise have been lost to fraud, over-payment or human error".
But he complained that despite championing anti-fraud measures, including data matching, central government was "still not sharing in the benefits" despite regular appeals.
He praised Sir Bob for ensuring the department he heads - communities and local government - was one of only two central government bodies, with the Highways Agency, to be directly involved.