The Queen's immunity from being called as a witness in a criminal court is to be reviewed by Parliament after criticisms of the royal role in the collapse of the Paul Burrell trial. The Lord Chancellor, Lord Irvine of Lairg, is to be questioned about the involvement of the monarch after the sudden acquittal of the former royal butler on Friday.
Senior government sources have revealed that Downing Street is "nervous" about the political fallout from last week's events. MPs will want to know what part the Attorney General, Lord Goldsmith, played in the decision to end the case.
The Crown Prosecution Service (CPS) called a halt after asking his advice on Monday. Lord Goldsmith will want to know at a meeting this week with the Director of Public Prosecutions, Sir David Calvert-Smith, why Mr Burrell's evidence about speaking with the Queen was not investigated further.
The late intervention by the Queen, whose recollection of a 1998 conversation with Mr Burrell led to the abandonment of the trial, raised questions over whether it should have gone ahead in the first place. He was accused of stealing more than 300 items from Diana, Princess of Wales, the Prince of Wales and Prince William.
Lessons will need to be learnt before a second royal butler, Harold Brown, goes on trial next month charged with stealing the Princess's property.
The Liberal Democrats said the Royal Family should consider paying some of the costs of the £1.5m case, as questions continued over the roles played by police, prosecutors and the monarchy. The police have been strongly criticised after revelations that they misled the Prince of Wales and Prince William over the extent of the evidence they had against the butler.
Simon Hughes, Liberal Democrat home affairs spokesman, called for a statement in the Commons. "Either the Royal Family or the Spencer family, or both, might think it would be fair and reasonable to ... make a contribution to the costs of the trial. The trial mostly concerned their families and their interests," he said.
Despite the demands for action, Buckingham Palace has ruled out an internal inquiry. "What happened is extremely clear," a Palace source said, adding that the decision to prosecute had been made by the police and CPS.
The Commons Public Administration Committee is poised to extend its investigation into the constitutional powers of the Royal Family. Brian White, a member of the committee, said MPs would want to "shine a light" on the justification for the raft of obscure powers of the Queen under the Royal Prerogative.
"We are looking at the Queen's role in relation to appointments and there is no reason why we shouldn't also look at her immunity in court," he told The Independent. "Court cases collapsing happens to ordinary people up and down the country every week, but ordinary people don't all have the Queen to come to their rescue."
Lord Richard, a former Labour leader of the House of Lords, called on the committee to examine the Queen's Crown immunity. "It's been a problem since 1911, when it was decided you couldn't put the monarch in the witness box," he said.
Lord Morgan, the historian and chairman of a Fabian Society Commission on the future of the monarchy, told Radio 4's The Westminster Hour: "I would think we ought to regard this extraordinary case, which has aroused so much attention for its sheer absurdity, as a step towards a written constitution making the monarchy accountable."
The Labour MP Dennis Skinner said he was writing to Lord Irvine about the Queen's role because there had been a "clear-cut case of withholding vital information before and during the trial ... At the risk of finishing up in the Tower, I cannot see why people, however high and mighty, should be allowed to escape the full rigour of the law." Several other Labour MPs are expected to table parliamentary questions on the trial.
Lord Carlile, Mr Burrell's counsel, said there was no doubtthe Queen had acted properly, if belatedly.