The announcement that the Palace is to hold an internal inquiry into the collapse of the Paul Burrell trial could leave it open to "whitewash" allegations, some MPs have warned.

The failure to order an independent inquiry could suggest there was something to hide, said Labour MP David Winnick - a member of the Commons Home Affairs Select Committee.

His comments came amid mounting criticism of the palace's decision among MPs.

If there is no external inquiry, then quite a lot of people will say there is something to hide

David Winnick, MP

Prince Charles has ordered an internal review into the way the trial of Princess Diana's former butler ended when the Queen came forward with vital information.

But the appointment of the prince's private secretary Sir Michael Peat as the head of the inquiry, and the fact that the Queen is not going to be involved has drawn criticism from MPs.

"If there is no external inquiry, then quite a lot of people will say there is something to hide when quite likely there is nothing to hide at all," Mr Winnick told BBC Radio 4's Today programme.

'Racing certainty'

The inquiry would do nothing to quell public suspicions that the Queen spoke up to prevent embarrassing revelations emerging when Mr Burrell gave evidence, the MP said.

Labour MP Dennis Skinner said he believed it was a "racing certainty" that Sir Michael would "find for the Palace".

The inquiry will also look at subsequent allegations after the trial's collapse, including a cover-up of a rape and the alleged sale of official royal gifts.

But the investigation will focus exclusively on the Prince of Wales' household and will not consider the Queen's role in the trial's collapse, nor the actions of the police or Crown Prosecution Service (CPS).

Earlier, Labour chairman of the Commons Public Administration Committee, Tony Wright MP, said the inquiry was not enough.

"I think things are so serious that responses like this show really how inadequate they are," he said.

There have been calls for an inquiry headed by a High Court judge that could look into all aspects of the affair, and that might attract more public confidence about impartiality.

'Allay suspicion'

The vice president of the Society of Labour Lawyers, Geoffrey Bindman, agreed that an internal inquiry would not satisfy public demands for credibility.

Speaking on BBC Radio 4's Today programme he said: "An independent person would carry more weight and allay public suspicion."

It is up to me to make sure that this office is whiter than white

Sir Michael Peat

He said although the palace could look into its own "domestic affairs", such an inquiry would not deal with issues such as the criminal justice system and the constitutional position of the monarchy.

"There needs to be an examination of the constitutional position of the monarchy in relation to the prosecution process," he said.

Even the Attorney General - the government's chief legal adviser who has responsibility over the prosecution service - is nominally the Queen's staff, he said.

The internal inquiry is to be conducted by the Prince's private secretary, Sir Michael Peat, with defence barrister Edmund Lawson QC.

Sir Michael said "in due course" an external inquiry may be held, but added that it could not be ordered by St James's Palace as it would involve other bodies, such as the police and Crown Prosecution Service.

Sir Michael will show 'neither fear nor favour'

He said: "We are looking at issues that took place here at the Palace. It is up to me to make sure that this office is whiter than white."

In a statement, Buckingham Palace said the Queen supported the inquiry being carried out by Sir Michael.

The palace has released the chronology of the Queen's involvement in the Burrell case.

The inquiry will examine four key questions:

• Was there any improper cover-up of the 1996 rape allegations?
• Was there anything improper or amiss in the conduct of the Prince of Wales's household with respect to the termination of the Paul Burrell trial?
• Have official gifts been sold?
• Have any members of staff been in receipt of improper payments or benefits?

Sir Michael insisted he would conduct the inquiry "vigorously and without fear or favour", and make the findings public.