'An abysmal, lacklustre, hapless lame duck' - secret US view of Gordon Brown

Then-US ambassador Robert Tuttle delivered a withering assessment of Brown's premiership, including the claim that Labour was experiencing "post-Blair rudderlessness" as his successor's vision failed to spark enthusiasm in the party.

Mr Tuttle's cables are among 250,000 secret documents obtained by Wikileaks and released onto the internet and to newspapers.

They show that the US embassy followed the travails of the Brown premiership closely and provided updates to the state department on his probable successors as Labour leader - apparently without spotting the man who eventually replaced him, Ed Miliband.

Following Labour's by-election defeat at the hands of the SNP in Glasgow East in July 2008, Mr Tuttle said: "As Gordon Brown lurches from political disaster to disaster, Westminster is abuzz with speculation about whether he will be replaced as prime minister and Labour party leader, and, if so, by whom.

"A terrible by-election defeat ... has left the Labour party reeling and fuelled fears among MPs that Brown's leadership of the party, and his premiership, may now be beyond repair."

One of the PM's closest lieutenants, Nick Brown, had briefed the embassy the morning after the Glasgow poll that the by-election result was "terrible" but that Mr Brown would be able to "slap down" any threat to his leadership.

Mr Tuttle reported signs of problems even earlier than this, at Labour's first spring conference under Mr Brown in 2008.

The conference was "characterised by low energy, poor attendance, and a lack of charismatic leadership", wrote the ambassador.

"The lack of energy that hung like a pall over the keynote speech was evident elsewhere, either because of low attendance or the party's financial woes ..." he added. "Even though Blair ended up unpopular, he was the sun around which the party orbited, and his speeches, no matter the content, sparked an emotional response.

"Brown's earnest and praiseworthy vision excites no opposition and yet it seems to excite no great enthusiasm either."

The only "star power for a party that seems increasingly to miss Tony Blair's charisma" was provided by then foreign secretary David Miliband, who produced a "palpable ... frisson of excitement" whenever he appeared.

During the financial crisis following the collapse of Lehman Brothers in autumn 2008, the embassy reported that the prime minister was "suddenly riding high".

However, by April 2009, following the resignation of aide Damian McBride over a plot to smear Conservative party figures, US officials judged the governing party was at such a low ebb that it was "unlikely that any Labour politician with his or her eye on the future would want to take on the sinking ship that is the current Labour party at this time of crisis".

An official predicted correctly that Mr Brown would be allowed to remain at the helm of the party until the general election and replaced shortly after Labour's defeat.