Sir John Bourn, the Government's spending watchdog, faced calls for his resignation today after new details of his expense claims were released.

Sir John has spent almost £27,000 in the past three years on dining out, including meals at some of London's best restaurants and hotels.

The comptroller and auditor general - responsible for investigating waste and extravagance in Whitehall - has also enjoyed the hospitality of major British firms including BAE Systems and IT contractor EDS.

Today's revelations follow the disclosure that Sir John had racked up a travel bill of £365,000 over the past three years. This included first-class travel with his wife to San Francisco, the Bahamas, Brazil, Lisbon and Venice.

The details of his expenses - released by the National Audit Office - prompted calls from opposition MPs for Sir John to consider his position.

According to the Audit Office, Sir John has enjoyed 164 lunches and dinners since 2004, including meals at the Ritz, Savoy, Dorchester, Wiltons, Mirabelle and Bibendum. The bills, nearly all for two people, vary from £80 to £301. The auditor general also visitedthe British Grand Prix as the guest of BAE systems; attended a polo match funded by EDS and visited the opera as the guest of GSL, a company promoting the public finance initiatives.

Sir John, 73, is a career civil servant who has worked in Whitehall for decades. Under his guidance, the National Audit Office has produced critical reports on the cost of the Olympics, government expenditure on IT projects and "unacceptable errors" in the tax credits system.

Kevan Jones, the Labour MP for Durham North, said: "Sir John is going to find himself in a very difficult position as the guardian of the public purse." His criticism was echoed by Norman Lamb, the Liberal Democrat health spokesman, who said Sir John should consider his position. "This behaviour is inappropriate and leaves him open to charges of conflict of interest," he said.

A spokeswoman for the Audit Office said Sir John would no longer take first-class flights or travel with his wife without parliamentary approval.

"We have decided to take the unprecedented step of volunteering all this information - even though nobody has requested all these details. We thought this would contribute to transparency and we intend to release all details of future expenditure on foreign trips and entertaining by Sir John and the senior management board of the NAO every six months." She added: "The auditor general justifies the dinners and lunches as part of the need for the NAO to keep in touch with a wide range of people, including companies that are doing business with government and the NAO."

Union leader Mark Serwotka, general secretary of the Public and Commercial Services Union, said: "Poorly paid civil servants who face losing their jobs due to so-called efficiency drives will be astounded at the amount spent on trips abroad and the inappropriateness of some of the lunches.

"With government departments facing budget cuts and slashing jobs over the next three years, you would think that those responsible for ensuring value for money would lead by example."