Beleaguered Gordon Brown suffered a fresh blow as a key Labour think-tank accused him of "neurotic under-confidence".
The Prime Minister worries too much about presentation and must "cancel Number 10's subscription to PR Week", according to the Fabian Society.
Strong and radical leadership was needed because Labour was "badly stuck" over how to win the next general election, the society said.
The damning critique was delivered by Sunder Katwala, the general secretary of the left-wing think-tank. It will be particularly stinging for Mr Brown as - like all previous Labour premiers - he counts himself among the organisation's members.
Amid flagging poll ratings and persistent sniping at Mr Brown's leadership, Mr Katwala warned that his administration "risks being written off before its first anniversary".
He insisted that the PM had to make his "core vision" clearer to show what Labour wanted to change, and reassemble a "winning electoral coalition".
"The challenge is not just one of communication but political strategy too," Mr Katwala said.
"Gordon Brown recognised last spring that 'more of the same' could not defeat the call of 'time for change' next time. He was right. But what three key points of 'change' could voters point to if asked at the end of his first year as Prime Minister in June?"
Mr Katwala insisted that the party's "internal debate" on strategy was "badly stuck".
"The Left worries that countering southern discomfort would cost Labour's soul; the Blairite right flank that appeasing Guardian reading liberals would lose the election. Labour won't recover by debating which voters it doesn't want."
