The Government is refusing to disclose David Cameron's bill for wining and dining celebrities, politicians and other prominent figures at his grace-and-favour country home.
The Cabinet Office insists "centralised" records mean it would be too expensive to provide details of the Prime Minister's spending at Chequers, and that of his Lib Dem deputy Nick Clegg at Chevening.
The refusal came after a Freedom of Information request by the Press Association, asking for official hospitality costs at the residences over the past five years.
A list of people hosted by the PM and Mr Clegg at public expense is published quarterly. The latest disclosure for January to March this year shows that Mr Cameron dined with the Queen and supermodel Claudia Schiffer among others.
However, no costs have been released for the hospitality. Under the Labour Government a global figure was issued for spending on official entertainment at Downing Street and Chequers, but that now appears to have been dropped.
Responding to the FoI request, the Cabinet Office said it did not keep material "in a way that readily facilities extraction".
"The information is not categorised by event as such, which means that it is not readily identifiable from the database which entry relates to what type of expense," the department said. "Attempting to fulfil your request would therefore mean searching through the records of individual transactions to identify which of those were in scope."
Andy Silvester of the TaxPayers' Alliance said the situation was "absurd".
"It will strike voters as thoroughly absurd that this information is difficult to find," he said.