Parliament's top spending watchdog has asked for access to details of investments that generate the private income of the Prince of Wales.

Auditor general Sir John Bourn told MPs he wanted to study the accounts of the Duchy of Cornwall, which last year provided the Prince with £11.9 million in revenue.

His request came as Bertie Ross, secretary and keeper of records to the Duchy, gave evidence to the Commons public accounts committee.

The Duchy's finances are audited privately by PricewaterhouseCoopers and approved by the Treasury.

"I would like to have a look at the books," Sir John told MPs. "That is not to take away the value of what Mr Ross provides to the Treasury.

"But the Treasury is part of executive government. My responsibility is to parliament."

Ross and Keith Willis, the Duchy's head of finance, received hostile questioning by Labour MPs.

The pair were accused by Alan Williams of "living in a closeted world".

"You take privilege for granted. It is like winning the lottery every year," he added.