Gordon Brown last night faced the first out-and-out call from a Labour MP to stand down as Prime Minister in the "best interests" of the party.

Gordon Prentice, a Scot who represents a North of England constituency, claimed that his leader lacked the "skills" for Number 10.

While he had "sympathy" for Mr Brown, last week's disastrous Glasgow East by-election result proved a change was needed.

As Labour in Scotland began the race to find a new Holyrood leader following Wendy Alexander's shock departure, the party as a whole was still coming to terms with its catastrophic defeat at the hands of the SNP and what it could mean for Mr Brown's future.

In the immediate aftermath of last Thursday's poll, Manchester MP Graham Stringer called for a leadership contest as did Paul Kenny, leader of the GMB union, implying that the PM should be challenged.

Yesterday, Ian Gibson, another Scot who represents Norwich North, insisted Mr Brown needed an "Obama moment" to reignite his premiership and that he had until September to come up with some "zippy policies" or face a challenge.

However, Mr Prentice, the MP for Pendle in Lancashire, was far more direct: "A prime minister needs a different set of skills from a Chancellor of the Exchequer. A prime minister must be able to communicate, persuade and enthuse. If not, the message is lost. I hope Gordon reflects on things during August and accepts that it is in the party's best interests, and perhaps his own, for him to stand down."

He added: "Politics is a rough old business. You have got to be able to paint a picture, you have got to be able to motivate people, and I do not think Gordon has those skills."

Tony Lloyd, Chairman of Labour MPs, claimed Mr Prentice's view was not widely shared by back-bench colleagues but he admitted there was a need for a "sharper focus" and for Mr Brown "to get across what he's all about".

Harriet Harman, the Leader of the Commons and Labour's deputy chief, again rallied behind Mr Brown, insisting Britain had "not yet seen the best" of the PM. "He is the solution, not the problem," she declared.

However, speaking on GMTV, she said: "I can recognise that I don't think the British people have seen the best of him yet as Prime Minister."

Home Secretary Jacqui Smith demanded that Labour MPs stop "talking among themselves" and back the leader.

While ministers continue publicly to back Mr Brown, a good deal of soul-searching is going on privately as MPs begin their summer holidays.

Reports have suggested disgruntled back benchers are to pen a letter to the cabinet urging it to spark a leadership contest in the autumn. If a coup were to be attempted, it could come from an unlikely rather than a likely source, possibly before the annual conference in Manchester towards the end of September.

Meantime, Lance Price, a former No 10 spin doctor, warned Labour was in "dire straits" and heading for a "catastrophic defeat" that could consign it to opposition for 15 years.