Senior figures at the heart of the British establishment were embroiled in a constitutional storm over the freedom of MPs after the Conservative Damian Green was arrested for obtaining leaked Whitehall documents.
Britain's top police officers, the highest-ranking parliamentary officials, senior civil servants and the Prime Minister faced a barrage of questions over the "heavy-handed" treatment of the shadow Immigration minister.
As the Conservative Party questioned who within the Metropolitan Police had authorised the raid and why the Commons authorities had permitted it, an opinion poll by IPM showed the Tories had surged to a 15-point lead over Labour, despite voter confidence in Gordon Brown's economic rescue package. The poll put the Tories on 45 per cent and Labour on 30 per cent.
Last night, Mr Green's wife told how her "blood ran cold" when nine anti-terrorism officers raided their home on Thursday and rifled through confidential papers while Mr Green was questioned for nine hours.
Fury grew over the disclosure that the Commons authorities had allowed police to take the unprecedented step of searching an MP's private office.
The raid at the Kent premises ended yesterday, with officers confiscating Mr Green's mobile phone, BlackBerry and computer files containing correspondence with his constituents. His email account was also disabled.
Gordon Brown and his ministers denied knowing that Mr Green was about to be arrested but the Tories claimed the Government had failed to answer accusations that Mr Green's detention had been politically inspired.
Nick Clegg, the Liberal Democrat leader, described the whole episode as "a may-day warning to democracy".
Backbenchers demanded an explanation of the role played by Jill Pay, the Serjeant at Arms in charge of Commons security, and Michael Martin, the Commons Speaker. The Tory MP for Lancaster and Wyre, Ben Wallace, wrote to Ms Pay: "The House of Commons and Palace of Westminster has in place certain safeguards to protect [members] from the excesses of the executive. It is most distressing, therefore, to find out that the House authorities allowed a search to take place."
Douglas Carswell, the Tory MP for Harwich, said: "If it turns out the Speaker of the House of Commons gave the go-ahead for this raid, I will be demanding to his face, on every occasion I can, that Mr Martin now quit."
The Labour MP David Winnick said the episode was "very disquieting".
The Tories asked who in Scotland Yard had authorised the operation. Police sources said the decision would have been referred to the acting Commissioner, Sir Paul Stephenson. Home Office leaks, such as the disclosure that 5,000 illegal immigrants had been cleared to work in security jobs, sparked the furore. Police arrested a junior Home Office official last week.
The investigation led officers to Mr Green on Thursday. He was arrested on suspicion of conspiring to commit misconduct in a public office and aiding and abetting, counselling or procuring misconduct in a public office.
His wife, Alicia, told friends how nine officers had looked "sheepish" as they had rifled through personal papers at the couple's home in west London, even examining letters she and her husband had exchanged as students, and leaving with three folders of bank statements.
She had feared her husband had been in an accident when the officers asked if there were children in the house before starting the search. Her teenage daughter had burst into tears when she had come home from school to see their home filled with police.
Mrs Green, a practising barrister, said she had stopped police taking the family computer because it contained confidential details about her clients.
The Tories denied Mr Green had offered inducements to a Home Office whistleblower. A party official said: "We want to make it clear there was no financial or any other inducement offered to anyone." David Cameron, the Tory leader, said: "If they wanted to talk to Damian Green, why not pick up the telephone and ask to talk to him? I think this is extraordinary that it was so heavy-handed."
Mr Brown said: "I had no prior knowledge, the Home Secretary had no prior knowledge, I know of no other minister who had ... prior knowledge."
Sir David Normington, the Permanent Secretary at the Home Office, said: "The Home Office has suffered a number of leaks of sensitive information over an extended period ... this was clearly a matter of serious concern in that it risked undermining the effective operation of my department."
A very leaky business
*1947 The Chancellor, Hugh Dalton, was about to give his Budget when he mentioned to a reporter that he would raise taxes on beer and on dog racing.
What happened next
The reporter rushed to a phone and got his story on the streets as the Chancellor was still speaking. Dalton quit the next day.
*1984 A senior MoD official, Clive Ponting, sent documents to a Labour MP contradicting the official story about the sinking of the Argentine warship, General Belgrano.
What happened next
Ponting argued that disclosure was in the public interest and was acquitted of breaching the Official Secrets Act.
*2000 A leaked memo from Tony Blair to advisers raised fears that his government was seen as "out of touch" on crime and asylum.
What happened next
Despite a hunt, the mole was never found.
*2004 A Sunday newspaper received Whitehall papers detailing Cabinet divisions over post-war strategy in Iraq and the introduction of ID cards.
What happened next After a police investigation, Claire Newell, who worked as a temp in Whitehall, was arrested and questioned about the leaks. She was later cleared.