EDINBURGH: Scottish leader Nicola Sturgeon said Saturday her scandal-hit predecessor's return to politics at the helm of a breakaway pro-independence party raised "significant questions" ahead of May elections.

But Alex Salmond's new Alba Party scored an early coup with the defection of a veteran lawmaker after more than 40 years in Sturgeon's Scottish National Party (SNP), giving Alba its first MP in the UK parliament in London.

Kenny MacAskill said he disagreed with the SNP's electoral strategy and endorsed Salmond's ambition to deliver a "supermajority" for Scottish independence in the coming elections.

At Friday's launch of Alba - the Scots Gaelic word for Scotland - Salmond said the party was not a direct challenge to the SNP and would urge people to vote tactically.

Sturgeon, however, accused her predecessor as SNP leader and Scottish first minister of acting out of "ego".

"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," she told reporters on the campaign trail.

"But that's for voters to judge and decide," Sturgeon added.

"Alex Salmond is a gambler. It is what he enjoys doing. But this is not the time to gamble with the future of the country."

Salmond, 66, was Scotland's first minister from 2007 to 2014. He stepped down and handed the reins to Sturgeon after losing a referendum on independence.