Confidentiality agreements between the BBC and top radio stars are preventing full scrutiny of the way it spends public money, a report from an influential group of MPs has revealed.

The House of Commons Public Accounts Committee said yesterday the BBC appeared to be paying some of its best known radio presenters, including Jonathan Ross, Chris Moyles and Sir Terry Wogan, more than twice what commercial stations pay theirs.

The BBC refused to provide the National Audit Office with a breakdown of presenters' salaries for a selection of radio shows unless the public spending watchdog signed a non-disclosure agreement, the committee said.

It spent £605m on its radio services in 2007/08, or around one fifth of its spending and was engulfed in controversy over the £18m deal over three years reportedly signed with Ross, who presents a Friday night TV chat show and Saturday show on Radio 2.

Radio 1 breakfast show host Moyles is said to be on £630,000 a year while Radio 2 star Wogan is reportedly paid an annual salary of £800,000. It took repeated requests to the BBC for it to reveal that Ross was paid £6m a year.

But while the salaries of Moyles, and Wogan have come under scrutiny and some of the money-spinning deals have been made public, it continues to refuse to disclose other salaries.

Around 40 BBC television and radio stars are reportedly earning more than £1m a year including Graham Norton, reputedly on £2.5m a year, and Jeremy Paxman, who is said to earn £1m a year.

Edward Leigh MP, the chairman of the committee, said it was "disgraceful" that the BBC could dictate what the watchdog could inspect when public money was at stake.

The report on the efficiency of radio production at the BBC said the government should arrange for the watchdog to have legally-guaranteed right of access to the BBC's expenditure, including presenters' salaries, as it does for other publicly-funded bodies.

Mr Leigh said: "The National Audit Office has a statutory right to examine the details of expenditure in any government department. It has no such right of audit access to the BBC, despite the fact that the corporation is funded with over £3bn of public money each year.

"One consequence of this highly unsatisfactory arrangement is that the BBC would not provide the head of the National Audit Office, the Controller and Auditor General, with a breakdown of the presenter and staff elements of radio programme costs, unless they agreed to constrain discretion to report to parliament on what they saw.

"Very few will find acceptable any such constraints on the National Audit Office's ability to investigate how a publicly-funded national institution spends our money. It is disgraceful that the National Audit Office's lack of statutory audit access to the BBC puts the corporation in the position to dictate what the spending watchdog can and cannot see."

The report found that programmes such as Wake Up to Wogan on Radio 2 cost on average twice as much per hour as the most expensive commercial breakfast show.

For the corporation's breakfast and "drivetime" shows, presenters' salaries accounted for around three quarters of the total staff costs.

The MPs said the BBC's main value for money test, the so-called "cost per listener hour", which takes the size of audience into account, risked creating an inflationary wage spiral, and should be balanced with a range of other measures.

While commercial stations had been cutting hourly rates for presenters in response to falling advertising revenues and an increasingly fragmented audience, the BBC had until recently been increasing its rates, the report said.

The BBC Trust, the corporation's governing body, said it was "disappointed" the NAO would not sign the non-disclosure agreement.

Jeremy Peat, a BBC Trustee, said: "The Trust is committed to ensuring value for money for licence fee-payers. That's why we have commissioned a series of such studies from the NAO and others."