Johann Lamont has resigned as leader of the Scottish Labour Party with immediate effect. She told the Scottish Daily Record:

“I am proud of what we have achieved over the last three years. We held Alex Salmond to account”

But was critical of some Scottish Labour colleagues, saying:

“colleagues need to realise that the focus of Scottish politics is now Holyrood, not Westminster.”

The BBC also reports Lamont accusing some in the party of trying to run Scotland “like a branch office of London”. A Labour source this evening told LabourList that Lamont “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 party well and we hope will serve the party again in the future.”.

Rumours of Lamont’s possible resignation as Scottish Labour leader had been circulating since before the Scottish Independence referendum with some even expecting Lamont to resign in the days immediately after the result – yet she had announced her intention to fight on.

Scottish Labour – facing a difficult and uncertain future – is now in search of a new leader.

Update: Here’s Ed Miliband’s statement on Lamont’s resignation:

“Johann Lamont deserves significant credit for the successful No vote in the Scottish referendum campaign. She campaigned the length and breadth of Scotland making the case for social justice within the United Kingdom. She has led the Scottish Labour Party with determination. I know she will continue to serve her constituents.”

Update II: Lamont leaves some parting shots in the full interview with the Daily Record, which is now online. She says that “some wanted me to become the issue”, moving the focus away from devolution and onto the subject of her leadership. Her decision to stand down is so that “the debate our country demands can take place.”

The next leader of the Scottish Labour Party does not have to be a member of the Scottish Parliament (MSP) yet, so long as they stand in the Holyrood elections in 2016. That means that a Westminster MP could stand, as long as they announced their intention to fight to become First Minister at the next Scottish elections.

Update III: Deputy leader to Lamont, and now acting leader of Scottish Labour, Anas Sarwar MSP has released a statement. In it, he praises Lamont’s handling of elections over the last three years, and says that the Party will not lose sight of fighting the Tories and the SNP:

“When the Scottish Labour Party needed someone to step up, the person who answered the call was Johann Lamont. Johann lifted the party when it needed it most, led the party to success in the 2012 Council elections, to by-election wins and, most importantly, to a successful referendum result which saw over 2 million people vote to remain part of the UK.”

“I want to thank Johann for all the support and advice she has given me over the past three years. I am clear she will continue to pursue with great vigour the causes close to her heart, causes which brought her into politics in the first place.”

“The Scottish Labour Party will now consider and set out in due course the process for electing a new leader as we continue to work to return a Labour Government at the General Election in 2015 and in the Scottish Parliament elections in 2016.”

“In the interim we will also not lose sight of the fact that under the Tories and the SNP inequality is rising, the number of children in poverty is going up, Scotland’s NHS is in crisis and college places are being cut and we will continue to hold both Governments to account.”

Update IV: Gordon Brown (himself a rumoured candidate) has released a short statement, praising Lamont’s “down-to-earth approach”:

“She brought determination, compassion and a down-to-earth approach to the leadership and deserves great credit for taking on the challenge after 2011.

“I wish her well in the future.”

Update V: The Scottish Secretary of Unite the Union, Pat Rafferty, has released a statement saying Scottish Labour must face up to the new political landscape:

“Johann Lamont’s departure must now spark the desperately needed process of renewal of Scottish Labour’s relationship with the people of this nation.

“Unite urges the party to take full and honest consideration of the recognisable concerns raised by Ms Lamont.

“Labour in Scotland must understand that there has been a seismic change in the political landscape in our country. People want a party that grasps this and has the vision to work with them to build the fairer nation they desire.”