David Blunkett will today make a statement to the Commons on the security debacle which led to an intruder sharing the stage with Prince William at his birthday party.

The Home Secretary ordered Met Police chiefs, responsible for policing Windsor Castle where the African-themed party was held, to have a report on his desk less than 48 hours after Aaron Barschak made his way with few hindrances to within metres of most of the royal family.

In his Commons statement today Mr Blunkett is expected to illustrate how the Met will avoid any further such occurances in future.

The incident has been compared in seriousness with the failure of police to prevent Michael Fagan entering the Queen's Buckingham Palace bedroom, while she was asleep there, and sitting on her bed in 1982.

Metropolitan Police Assistant Commissioner David Veness made a statement to the press yesterday in which he called the breach at Windsor Castle 'wholly unacceptable' and 'a matter of great regret'.

He continued: "The Commissioner has tendered apologies to the Royal Family for the appalling breach of security at Windsor Castle on Saturday evening."

Mr Veness described how police believe Aaron Barshak entered the castle, dressed as Osama bin Laden in drag.

He said: "It appears that the intruder gained access to the Castle precincts by scaling an embankment, climbing a tree, jumping onto a wall and then reaching a terrace.

"He was challenged by a contractor and escorted to a police point. He gave what appeared to be a credible story and was allowed into the area of the castle where the party was taking place."

It is thought that the centre of further investigation may be Commander Peter Loughborough, an earl who studied at Eton, who is head of security for the royal family.

The earl rose through police ranks to be promoted to the royal job as a means of calming difficult relations between the Met and the royal family after the disastrous trial of Paul Burrell, Princess Diana's former butler.