WENDY Alexander was under pressure to resign last night after she issued a statement reversing her U-turn on an independence referendum.

The Labour leader was said to have been described as “mad” by her predecessor Jack McConnell ahead of the humiliating climbdown that threatens to bring her party to its knees.

She has also been criticised by Henry McLeish, the former first minister, and John Prescott, the former deputy prime minister.

In the worst week of her political career, Alexander was accused of treachery by other unionist parties and infuriated Gordon Brown, her political mentor, after she unilaterally abandoned Labour's long-held opposition to a vote on separatism.

She had sought to embarrass the Scottish National party into bringing its plans for a referendum in 2011 forward, but the strategy backfired.

Yesterday, following a meeting of Scottish Labour's ruling national executive committee, she attempted to extricate herself from the mess. A statement issued on her behalf suggested Labour could no longer be guaranteed to support a referendum, despite her party offering an assurance earlier in the week that it would.

She had threatened to introduce her own referendum bill at Holyrood, despite the standing orders of the parliament preventing her from doing so because the SNP government is already committed to legislating on the issue. “The SNP have now made clear they will block any referendum bill Labour might have introduced,” her statement said.

“Labour were aware of the parliament's standing orders, but we underestimated the SNP's desperation to use any device to avoid facing the verdict of the Scottish people. The SNP have therefore now blocked this route in the Scottish parliament.”

Last night Nicola Sturgeon, deputy leader of the SNP, described the latest twist in the saga as a “humiliating climbdown”, adding “words like ‘laughing stock' do not even begin to reach the extent of the Labour party's disarray. The abject humiliation of this climbdown statement leaves Wendy Alexander without a thread of credibility and her position as Labour leader now looks impossible.”

Annabel Goldie, leader of the Scottish Conservatives, said: “This must go down as one of the most extraordinary, humiliating press statements ever issued.”

McConnell, a former Labour first minister and boss of Alexander, has told friends that he thinks she is “off the wall”.

“He isn't surprised that this kind of thing has happened. He sees this as all Wendy's madness and him [Brown] being unreasonable,” said one. “He says Gordon was impossible to deal with and he regards Wendy as being off the wall. He thinks she's just not got any judgment.”

Another friend said: “Jack thinks the referendum policy is a mess. It just proves what he has thought for years, that she's mad and he [Brown] is a nightmare.”

Speaking on BBC Radio Scotland today, McConnell will say: “What both Wendy and Gordon need is to be able to move on with a clarity about what each is saying.”

McLeish accused Alexander of presiding over “a difficult year of ineffective opposition” and warned that her support for a referendum was damaging the party.

Prescott said her referendum plan was flawed from the start because Holyrood does not have the power to run a legally binding referendum.

“The decision belongs to the House of Commons and not the house of Wendy. Wendy has the job of determining strategy in Scotland with the SNP, but you can't suggest that we in Scotland will bring in legislation - that is a UK decision that belongs to us all.”

Several Labour shadow ministers were privately appalled by Alexander's sudden conversion to the case for a referendum, claiming it would have played into the hands of the nationalists.

They believed that, at best, it would have led to a “no” vote on independence and the SNP putting the issue to another referendum. At worst, it could have led to a “yes” vote.

Last night a growing number of Labour MPs were saying she should resign. They fear her actions are jeopardising their chances at the next general election.

“She has to go, frankly. The one thing that was keeping her in her position was the lack of a good alternative. Now any alternative would be better,” said one.

“Every time she opens her mouth, she damages the party more. If she went, there would be a big sigh of relief among my colleagues.

“She's screwing up election chances in England as well as Scotland. It's up to people like Andy Kerr and Iain Gray to come to the aid of the party. I'd take anyone but Wendy. She's been cataclysmic.”

Alexander is facing a new fight with Brown this week over free personal care for the elderly. Her MSPs are expected to endorse a demand from the SNP that Westminster reinstates attendance allowances worth £30m a year.

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