NICOLA Sturgeon has called on former minister Mark McDonald to quit Holyrood and allow his constituents to elect somebody else.

The former Scottish Government children's minister was at the centre of an SNP investigation involving a series of complaints made by women, as a sexual harassment scandal hit politics and public life.

Earlier, McDonald announced he was quitting the SNP to continue as an independent MSP at Holyrood. But Sturgeon said that wasn't good enough.

"My view is clear," she said. "He was elected as an SNP MSP. If his behaviour is such that he himself considers he cannot continue as an SNP MSP, then it would be appropriate to give his constituents the opportunity to elect a new MSP."

The First Minister said the party could not force Mr McDonald to resign as an MSP, and it was therefore "a matter for him".

READ: Mark McDonald's full statement as he leaves the SNP

In a statement issued in Aberdeen this afternoon McDonald said he has tendered his resignation from the party and would return next week to the Scottish Parliament as an independent MSP.

Telling journalists he had advised the party of his immediate resignation as a member, he said: "I have further advised the parliamentary authorities that I will return to Holyrood next week to sit as an Independent MSP."

He has not voted or spoken in the Scottish Parliament since resigning from his post at the beginning of November last year, saying that "some of my behaviour" had "been considered inappropriate".

It emerged in the following days the behaviour in question related to text messages he had sent to a woman.

Two weeks later he was suspended by the SNP from the party after "new information" arose about his conduct, also relating to text messages.

And last month it emerged a further complaint had been made by another woman about his behaviour and that the SNP had hired a team of private detectives to investigate. It is understood a total of four complaints had been made against him.

Reports have suggested the SNP group of MSPs were expected to vote soon on whether to allow him back into the party.

Chief whip Joe Fitzpatrick was expected to summarise the investigation's report before the MSPs voted on whether to allow him back in to the group.

Following his long absence from Holyrood, opposition politicians had called for the 37-year-old, who had been regarded as a high-flier in the party, to return to the Scottish Parliament or quit his Aberdeen Donside seat.

McDonald was first elected to Holyrood as a list SNP MSP for the North East in 2011, but following the death of Brian Adam in April 2013, he was selected as the SNP candidate for Aberdeen Donside and resigned his North East seat to fight the by-election.

He held the seat for the SNP and was returned to the Scottish Parliament in June 2013. He then held the seat in the 2016 Holyrood election winning 56 per cent of the vote and increasing the SNP majority to 11,630 – the largest majority in the whole of Scotland.

Following Nicola Sturgeon's reshuffle in May 2016, he was appointed minister for childcare and early years. In this role he was responsible for the launch of the high-profile baby box policy. He was replaced by Maree Todd as childcare and early years minister.

Commenting on Mark McDonald's decision to resign as an SNP MSP but remain as an independent MSP, Labour Parliamentary Business Manager Rhoda Grant said: "Mark McDonald decided his conduct was not fit for a minister or an SNP MSP – but somehow it is acceptable for an MSP without party affiliation.

"People in Aberdeen Donside will rightly question that. It looks like Mark McDonald has put the reputation of the SNP before what is best for his constituents.

"The message from this statement today is that Mark McDonald considers the reputation of the SNP more important than the standards expected of an MSP."