Nicola Sturgeon has said there are "significant questions about the appropriateness" of Alex Salmond’s return to Scottish politics, after the former first minister announced the launch of his new party.
Former SNP leader Mr Salmond confirmed he will be standing for the Alba Party - a new pro-independence party - on the North East regional list section in May’s Scottish Parliament election.
On Saturday the party claimed its first big name defector from the SNP after MP Kenny MacAskill, a former Scottish justice secretary, announced he was joining Mr Salmond's new venture.
Former SNP councillor Chris McEleny is also standing as a candidate for the new party.
Speaking on the campaign trail on Saturday, Ms Sturgeon said: "I take no pleasure whatsoever in saying this but I think there are significant questions about the appropriateness of his return to public office given the concerns that have been raised about his behaviour previously but that's for voters to judge and decide.
"This is an election. We live in a democracy. For my part, in this campaign, I am focused on the interests of the country."
Last year Mr Salmond was cleared after a criminal trial of a series of allegations, including a charge of attempted rape.
The timing of the launch of the party comes amid a turbulent period for current first minister Nicola Sturgeon which saw her survive a vote of no confidence, cleared of breaking the ministerial code, but found to have misled Holyrood.
In response to Mr MacAskill's departure, the SNP said it was "somewhat of a relief" and called for a by-election.
The party’s Westminster leader Ian Blackford said: "After yesterday’s events this is the second least surprising news in Scottish politics.
"He has been an increasing embarrassment to many in the SNP and his departure is somewhat of a relief.
"That he is joining a party with serious questions to answer about its leader’s suitability for public office is no surprise.
"He should now resign his seat in the House of Commons to let a by-election take place immediately so the people of East Lothian can elect a new MP who will focus on their interests, rather than self-interest."
Launching the new party in an online event on Friday, Mr Salmond said: "Today Alba are hoisting a flag in the wind, planting our Saltire on a hill. In the next few weeks we will see how many will rally to our standard."
Mr Salmond said his party would be carrying a "positive" campaign and urged voters to back the SNP or another pro-independence party in the constituency seats.
The Alba Party will only be standing candidates in the regional lists in an attempt to boost separatist numbers in Holyrood.
In response to the formation of the new pro-independence party, the Scottish Conservatives said their leader Douglas Ross was seeking urgent talks with the leaders of the other pro-UK parties - calling on them to unite and work together to stop pro-independence parties winning a majority at Holyrood.
Mr Ross said the action was needed after Alex Salmond was unveiled as the leader of the new Alba Party – which is aiming to win seats on Holyrood’s regional lists to create a “supermajority” in favour of Scotland quitting the UK.
Scottish Liberal Democrat campaign chair Alistair Carmichael however insisted that the Tory leader’s politics were "far too dark and divisive".
Mr Carmichael said: "Lib Dems will work with others to deliver a constructive and ambitious plan for recovery, but Douglas Ross’s politics are far too dark and divisive.
"We will focus on winning seats and ensuring that the next government is focused on putting the recovery first, not independence."
Scottish Labour leader Anas Sarwar said Mr Ross "needs to grow up".
He said Mr Ross "needs to recognise that we are in the middle of a pandemic."
"He needs to recognise that this election is not some kind of game, it’s not some kind of battle, it’s not about party politics, it’s not about individual politicians fighting with each other – it’s about focusing on a national recovery."
The Scottish Greens criticised the new party as a “fringe movement”.
Listen to our politics podcast Calling Peston: