Alex Salmond has claimed there is "no obvious successor" to Nicola Sturgeon after Scotland's longest-serving First Minister announced her resignation.
The news sent shock waves through Holyrood and Westminster and saw party leaders from across the political spectrum pay tribute to the SNP leader's years of public service.
Salmond, who mentored Sturgeon during her early years in the party, warned her exit from frontline politics left Scottish independence with "no clear strategy".
He served as SNP leader in two spells until stepping down in the wake of the 2014 independence referendum.
Salmond said: "There has been no question of Nicola’s talents as a first-rate political communicator and election winner and – having been there – I feel for her personally on the day of her resignation.
"There are two questions for the future.
"One is that the movement has been left with no clear strategy for independence. The previously accepted referendum route has been closed and the de facto referendum/election proposal is now, at best, up in the air.
"Secondly there is no obvious successor. There are a range of able people in the SNP but they will now be tested in the fire of leadership inheriting a range of serious Government policy challenges.
"It is to be hoped that those voices which wish to reunite the national movement emerge to win that contest."
Keir Starmer, the UK Labour leader, wished the First Minister well and said she served "with dedication and passion" since she entered Bute House in 2014.
Rishi Sunak, the Prime Minister, thanked Sturgeon "for her long-standing service" and wished her "all the best for her next steps".
Michael Martin, Ireland’s deputy leader and foreign affairs minister, said: "Over many years, Nicola has demonstrated strong leadership rooted in her vision for Scotland.
"Ireland and Scotland are close neighbours and friends, and I have greatly appreciated and valued my regular engagement with the First Minister, particularly at British-Irish Council summits.
"I want to wish her all the best and look forward to engaging with her successor in due course," he said.
Anas Sarwar, the Scottish Labour leader said Sturgeon had led Scotland through some of the most "challenging times" in recent history.
"It is right that we pay tribute to those achievements, particularly during the pandemic," he said.
"Regardless of our differences, she is an able politician who has stood at the forefront of Scottish politics for more than 20 years. On a human level that is worthy of respect and thanks.”
Sarwar said Sturgeon had "secured her place" in history and he had "never for a moment doubted" her passion for Scotland.
He added: "All too often it is easy to forget that those on the frontline of our politics carry a heavy burden – not only for themselves but for their friends and families.
"I – and my entire party – wish her the best in whatever she does next."
Humza Yousaf, a potential candidate to replace Nicola Sturgeon as SNP leader, has said he is “gutted” to see her standing down.
The Scottish health secretary tweeted: "I have had enormous pleasure of being in her Government for the time she has been First Minister, and I can safely say she has always put interests of the country first, and governed for all of Scotland.
"She is right, politics can be brutal, it impacts on our relationships, our families and of course on our own physical and mental health. I hope the FM gets to experience some kind of normality upon standing down, she certainly deserves it.
"From leading our response to the pandemic to leading the independence movement to new heights, and many achievements in-between, Nicola Sturgeon should be very proud of what she has achieved as First Minister."
Ian Blackford, the former SNP leader at Westminster, hailed Sturgeon as "the finest First Minster Scotland has ever had".
The MP added: "When Scotland wins independence, she will have been its architect and builder. She has laid the foundations we all now stand on. We owe it to her to finish the job."
Scottish Conservative leader Douglas Ross MSP said Nicola Sturgeon “refused to accept the result” of the 2014 independence referendum and said her tenure as First Minister was marked with “relentless agitating” for another referendum.
He said: “Whatever our differences, it is right we recognise that political leadership is always demanding and takes its toll on a person and their family.
“I am glad Nicola Sturgeon has recognised this is the right time to go.
“However, at this time, we cannot ignore that she has presided over a decade of division and decay in Scotland.
“Instead of trying to unite the country in the wake of the 2014 referendum, Nicola Sturgeon refused to accept the result."
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