It's not just Roy Hattersley who'll shoot himself

John Reid must not become leader of the Labour Party. This pugnacious product of the Lanarkshire Labour badlands is temperamentally unsuited to the role of Prime Minister. He is an aggressive and unstable character who thrives on confrontation and conspiracy. The thought of John Reid with his finger on the nuclear button is frankly terrifying.

This is the politician who thought it was appropriate to spend three days in a luxury hotel with Radovan Karadzic. He famously punched a House of Commons attendant in 1991 during his years as a violent alcoholic. But giving up the bottle didn’t tame his temper. He nearly came to blows with the late Donald Dewar - no pugilist he - over the so-called “lobbygate affair” in 1999. The next First Minister, Henry McLeish, described Reid as a “patonising bastard”.

Reid’s son Kevin, who working for the firm Beattie Media, had been secretly taped boasting of his access to ministers. Kevin Reid’s subsequent employment as a parliamentary researcher led to the astonishing confrontation between the then Northern Ireland Secretary and the parliamentary standards commissioner, Elizabeth Filkin.

She accused John Reid of intimidating witnesses and attempting to undermine her inquiries. She even had tape recordings of Reid browbeating the former general secretary of the Scottish Labour Party, Alex Rowley into committing perjury.

Ms Filkin - who subsequently resigned - said "the conduct of Dr Reid caused serious and increasing concern" and it has continued to do so. He has been in eight ministerial posts in his post-alcoholic career each more disastrous than the last.

When he was at health he negotiated the disastrous consultants pay deal which, with the parallel GP contracts, has been a major cause of the current financial crisis at the NHS. At defence he famously attacked “rogue elements” in M15 and M16 and said that British soldiers in Afghanistan would “return without firing a shot”.

Now at the Home Office, he claimed that the department was “not fit for purpose” and promised to fire senior civil servants over illegal immigration. However, he has not succeeded in tracking down the foreign prisoners released without being assessed for deportation - the reason for his predecessor, Charles Clarke’s removal. The issue has been quietly dropped.

Instead, Reid has done what he has always been best at - being Tony Blair's attack dog. Mouthing slogans about “the presumption of deportation”, attacking civil libertarians, confronting British Muslims, and enthusiastically fronting the latest round of anti-terror legislation including 90 day detention.

. Most didn’t notice, but in his farewell speech Tony Blair set out Reid’s leadership prospectus by saying that Labour should attack David Cameron for being soft on criminals and too anti-American. This was a direct appeal to Reid as the only man willing to take on the Tories from the Right, rather than the Left.

Tony Blair was extravagant in his praise for Reid conference speech, the opening bid in Reid’s campaign for the leadership. But if Labour installs him as its leader, the party will complete its transition to an authoritarian party of the populist right. It will mean riots at home; new wars abroad. There will be imprisonment without trial, a massive increase in police powers, curbs on immigration.

This must not happen. If Reid becomes leader, I will be voting for David Cameron.