SCOTTISH Labour are in turmoil this morning after Johann Lamont ended weeks of speculation about her political future and resigned as leader.

Ms Lamont, who had been facing growing internal criticism since the independence referendum, said her decision would allow the "debate our country demands" about more devolution to take place.

The fight to replace her could now involve former Scottish Secretary Jim Murphy and former Prime Minister Gordon Brown, who led the campaign to ensure the Westminster party leaders stick to their pre-referendum pledge to give Scotland more powers.

Another contender is Anas Sarwar MP, Ms Lamont's deputy, who will step up to the leadership on a temporary basis. An MSP will also be chosen to stand in for Ms Lamont at Holyrood until a successor is elected.

Ms Lamont said she was proud of what the party had achieved over the past three years and that she had held Alex Salmond to account, but she hit out at internal Labour sniping about her leadership.

Ms Lamont also criticised party bosses in London for not allowing ­Scottish Labour more autonomy.

She accused some of her colleagues of trying to run the party in Scotland "like a branch office of London".

Ms Lamont believes some Labour MPs at Westminster are too concerned about their own interests and need to realise that the focus of Scottish ­politics is now Holyrood, not Westminster.

Ms Lamont, who replaced Iain Gray as leader in December 2011 following Labour's defeat at the hands of the SNP in the Scottish Parliament elections, said she was proud of her achievements. But her decision angered former Labour First Minister Lord McConnell, who said she had been pushed out. He tweeted: "This is a truly astonishing development. Johann leaves with head held high. Outrageous treatment of Scottish Labour Party leader."

The new leader will have the job of taking on First Minister elect Nicola Sturgeon in the run-up to the May 2016 Scottish Parliament elections.

Pressure from colleagues at both Holyrood and Westminster who were unhappy with Ms Lamont's leadership performance, together with bad poll ratings, are thought to be behind her decision.

The loss of ground to the Nationalists in the referendum in some traditional Labour heartlands, most notably Glasgow and North Lanarkshire, which both voted Yes, also alarmed colleagues.

A senior source close to Labour leader Ed Miliband said: "She realised it was time for a change in ­Scotland. She has put the party first. Ed regards her as an honourable woman, who has served the party well and we hope she will serve the party again in the future."

Following the referendum, Scottish Labour MPs have keenly encouraged Mr Murphy, the Shadow International Development Secretary, to consider replacing Ms Lamont.

However, the East Renfrewshire MP has insisted he would not move against his colleague. It would require a Holyrood by-election, which would be fiercely contested by the SNP.

Senior sources have talked up Mr Brown's return to the frontline given his barnstorming performance during the referendum. This is despite the fact the Kirkcaldy and Cowdenbeath MP has made clear he has no intention to return to frontline politics.

Sources also suggested Ian Price, General Secretary of the Scottish party, will announce his resignation today because of a lack of support from senior colleagues. One highly placed source said: "This is very much Ian's decision."

The party's referendum campaign highlighted internal problems, and senior party figures were dissatisfied with the organisation and administration of the Scottish party, including the press operation. Despite vowing to stay on as leader in the wake of the referendum, Ms Lamont is said to have become tired by infighting over her leadership and meddling by the UK Labour Party.

At the first session of First Minister's Questions she rebuked Alex Salmond for suggesting she would soon be out of a job, saying: "When the First Minister is long gone I will still be doing my job on behalf of the people of Scotland."

Ms Lamont faced calls to step aside after what was seen as a weak performance in the campaign, especially when she appeared in TV debates with Deputy First Minister Nicola Sturgeon, who is to succeed Alex Salmond next month as SNP leader and First Minister. A new contest will be a blow to the UK party so close to the General ­Election in May 2015.

Ms Lamont said: "I firmly believe that Scotland's place is in the UK and I do not believe in powers for power's sake. For example, I think power should be devolved from Holyrood to communities. But colleagues need to realise that the focus of Scottish politics is now Holyrood, not Westminster."

Ms Sturgeon tweeted that she wished Ms Lamont well but added that if reports of divisions between the Scottish and UK Labour parties were accurate then "@scottishlabour really is in meltdown".