David Blunkett has expressed "deep regret" at the "serious breach" of security during Prince William's 21st birthday party at Windsor Castle.
Mr Barschak said he was surprised by security
The home secretary had earlier warned that those involved in counter-terrorism and personal protection had their "heads on the block" after Aaron Barschak managed to gatecrash Prince William's celebrations at the Queen's Berkshire home.
In a statement to the House of Commons Mr Blunkett said he was determined that lessons should be learnt from the incident in which Mr Barschak had got "unacceptably close" to Prince William.
"Mr Barschak's actions have exposed an appalling failure in the security at Windsor Castle which simply should not have happened," he said.
Mr Blunkett said a report into the incident would be published in four weeks following an investigation by a senior commander from the City of London Police.
It's my job to make
sure that what happened at the weekend never happens again
Conservative home affairs spokesman Oliver Letwin suggested that the breach demonstrated the need for a minister in charge for homeland security who could devote all his time to such issues.
The lapse was an "important metaphor for wider failure", he said.
"You are too
busy. Too busy to wake up each morning, and to go to bed each evening worrying
exclusively about the systems of civil protection in this country," he told Mr Blunkett.
Metropolitan Police Commissioner Sir John Stevens said officers were "devastated" by the security lapse and he pledged that lessons would be learned.
In a newspaper interview, Mr Barschak - a stand-up comedian who had dressed as Osama Bin Laden for the stunt - told how he kissed the prince on both cheeks.
Mr Blunkett said he could not confirm that detail but he said a contractor in the grounds of the castle led the self-styled "comedy terrorist" to the main entrance to the party at the request of a police officer who was unable to leave his post.
Mr Barschak was in fancy dress and appeared to be slightly drunk.
According to the Daily Mail interview, the comedian wandered around the castle's grounds for almost an hour.
The police officer he spoke to helpfully gave him directions to the celebrations after accepting Mr Barschak was a drunken guest who had become lost.
"The security was non-existent", he told the paper.
"I was carrying a bag which could have had a bomb in it.
"I was just yards away from the Queen and Prince Charles.
"If I had been a real terrorist the entire Royal Family would have been wiped out."
Inside the party, the comedian delivered his comedy routine before heading towards the bar where he was challenged and then arrested.
He has now been released on police bail and will have to wait to find out whether he will face charges.
"Let's make it absolutely clear, the royal protection department, which makes
up part of the Metropolitan Police Service, is devastated by what took place at
Windsor Castle over the weekend," said Sir John.
"We have got to pick up the pieces of what's going on. It's my job to make
sure that what happened at the weekend never happens again."
Mr Barschak said the crowd listening to William at the event laughed at the comedian's appearance and applauded him out of the room once he had finished.
Barschak climbed over a wall and talked his way into the party
The paper said the comedian had been preparing to return to north London when he saw his opportunity to gain access to the castle, noticing an embankment on the north side of the building.
Mr Barschak climbed the embankment and then went up a tree next to the perimeter wall, before dropping over it.
He was spotted wandering around by a contractor, who assumed he was a guest and took him through a gate to a nearby police officer.
The comedian told the paper: "The whole time I was inside the castle, I was expecting to trip an alarm, to be picked up on CCTV, or to be confronted by a policeman."