Civil war in Iraq is more likely than a successful transition to democracy, according to Britain's senior envoy to the country.

William Patey, the British Ambassador to Iraq since last summer, gave his grim assessment in a confidential memo to ministers and senior military commanders that also predicted the break-up of Iraq along ethnic lines and instability in the country for the next five to ten years.

Details of Mr Patey’s final diplomatic telegram from Baghdad, which was sent last week, were leaked to the BBC, which reported extracts this morning.

"The prospect of a low intensity civil war and a de facto division of Iraq is probably more likely at this stage than a successful and substantial transition to a stable democracy," wrote Mr Patey in the cable, which was addressed to the Prime Minister, Foreign Secretary, Defence Secretary, Leader of the House of Commons, and senior military officers.

He went on: "Even the lowered expectation of President Bush for Iraq — a government that can sustain itself, defend itself and govern itself and is an ally in the war on terror — must remain in doubt."

Although Mr Patey, a former head of the Foreign Office's Middle East department and Ambassador to Sudan, said "the position is not hopeless" in Iraq, he said the country was likely to remain "messy and difficult" for the next five to 10 years.

The former ambassador expressed particular concern about the uncontrolled rise in sectarian killings and spread of ethnic militias in Baghdad and beyond that are thought to be killing an average of 100 Iraqis per day in bombings and drive-by shootings.

Last week, the US military estimated that as many as 40 Iraqis are also kidnapped every day. Many more Iraqis have died in casual, unchecked violence in the last three weeks than during the conflict between Israel and Hezbollah in southern Lebanon.

Mr Patey referred to the increasing power of Jaish al-Mahdi, also known as the Mahdi Army, the well-armed Shia militia led by the radical young cleric, Hojatoleslam Moqtada al-Sadr.

"If we are to avoid a descent into civil war and anarchy then preventing the Jaish al-Mahdi from developing into a state within a state, as Hezbollah has done in Lebanon, will be a priority," he said.

The BBC reported today that it has also learnt from military sources that British troops in Basra, where Shia militias are believed to control much of the local police force and government, are planning to dramatically step up operations against gunmen.

But Mr Patey warned ministers that British forces "can’t confront the militias alone" and that they needed the extensive co-operation of Iraqi police and soldiers.

He also urged the Government to beware of "too much talk of an early exit from Iraq" as this would weaken attempts by American and British troops to control the violence.

Mr Patey finished his posting last week and handed over to the new ambassador, the Honourable Dominic Asquith, who since 2004 has been the director of Iraq at the Foreign Office.

An outspoken Arabist, Mr Patey has made blunt statements about the coalition mission in Iraq before -- last week he told the BBC that there was "a fine line between pessimism and optimism" and that Iraqis had lost confidence in the police.

His remarks did not surprise former diplomats today, but opposition MPs highlighted the contrast between the former ambassador's outlook and the cautious optimism of Downing Street and the Foreign Office.

Michael Moore, the Liberal Democrat foreign affairs spokesman, told the BBC's Radio 4 Today programme: "I think this is the raw truth and it is in sharp contrast to the public statements of our own Prime Minister and of senior Iraqi politicians who have been highlighting some welcome security developments in recent days.

"Nobody has been drawing attention to the still parlous security situation in the country and the desperate way in which the country is still trying to get back on its feet after the war three years ago.

"We need a strategy. At the moment, there is no clear strategy from our Government or from the Americans, apart from a hope that things will get better."

Oliver Letwin, the Conservative head of policy, demanded more transparency from the Government about the state of the unrest in Iraq: "We need a frank assessment from the Government and the Government needs to be very open with all of us about all the information it has received and what it really believes the position to be in Iraq.

"We are all in this together and we can’t act together and do the right things unless we know what is really going on."

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