DEREK Mackay has been branded "predatory" amd urged to resign as an MSP after apparently grooming a 16-year-old schoolboy on social media.

Scottish Tory leader Jackson Carlaw said the former Finance Secretary had yet to fully account for the “colossal lapse of judgment” that led to his resignation from the Scottish cabinet this morning.

Scottish Labour leader Richard Leonard said: “Derek Mackay has acted beyond ‘foolishly’, his actions are predatory and must be thoroughly investigated. He has abused his position of power with a vulnerable adolescent.

“The thoughts of everyone at Scottish Labour are with the schoolboy involved and his family.

"The nature and the gravity of these allegations demands decisive action."

Scottish Liberal Democraat leader Willie Rennie also said it was a "troubling series of events, and not just for the family" of the boy, and that Mr Mackay had to go.

He said: "It's about the standards we expect as an MSP. Derek Mackay has not behaved in the way we would expect. It's time for him to resign."

Green co-leader Patrick Harvie added: "Derek Mackay’s behaviour was utterly unacceptable, and his resignation was clearly necessary."

Mr Mackay quit just hours before he was due to deliver the Scottish budget after the Scottish Sun printed hundreds of messages he sent the boy in recent months.

Mr Mackay was unaware of the boy’s age when he first made contact and called him “cute”.

Mr Carlaw said: “I think there will be parents who are concerned to know whether this boy is the only example of any social media contact that Mr Mackay has had.”

Mr Mackay, 42, announced he was gay in 2013 after leaving his wife.

In his resignation statement, he said: “I take full responsibility for my actions. I have behaved foolishly and I am truly sorry.

“I apologise unreservedly to the individual involved and his family.”

Ms Sturgeon accepted his resignation and said public finance minister Kate Forbes

rbes would deliver the budget later today instead.

However there are now calls for the SNP to remove the whip from Mr Mackay.

In November 2017, SNP childcare minister Mark McDonald quit after sending a handful of inappropriate text messages to an SNP colleague.

Ms Sturgeon later called on the Aberdeen Donside MSP to resign from Holyrood.

Mr Carlaw said the McDonald case had set a precedent for Ms Sturgeon to follow.

Speaking to the media at Holyrood, he said: “It’s not just a blow to the Scottish Government. It’s blow to the reputation of the Scottish Parliament and to politics in Scotland generally.

“It’s difficult to see, having read the material that’s now in the public domain, that this is another other than a colossal lapse of judgment by Derek Mackay.

“In any definition that you head of grooming on social media, what I’ve read it would appear to fulfill that definition and criteria.

“It seems very difficult to me to believe that Nicola Sturgeon simply believing that accepting his resignation from the government is in any way a line that can be drawn under the matter.”

Asked if Mr Mackay should resign as an MSP, Mr Carlaw said: “We obviously have the precedent that was set only a couple of years ago when another minister in the government was found to have behaved inappropriately.

“I think there will be parents who are concerned to know whether this boy is the only example of any social media contact that Mr Mackay has had.

“I’m dismayed. Derek Isn’t someone I’ve ever had any active dislike for in politics at all.

“He’s one of those who has had an appeal across all parties on a personal basis.

“But unfortunately that cannot excuse in any way at all what is a colossal lapse of judgement on his part and the consequences that follow from that.

“All of us in Scotland who take a stand in parliaments like this on this very issue will realise the enormous damage that it potentially does to politics to all parties and to the reputation of this parliament. I’m very  concerned about that.

Asked if the police should be involved, he said: “As I understand it, this boy is not underage, so I’m not sure whether any criminal offence has been committed. 

“I don’t know what further information we might find out.

“That really is the central issue. A senior member of the government, who stands as an example to many people, and in a parliament where we have taken a stand on this very issue, where precedents have previously been set, simply to accept his resignation from government and thank him for everything he did when he was a minister, seems to me to fall short of an adequate response. [Losing the whip] is the precedent that has been set.”

Asked again if Mr Mackay should quit as an MSP, he said: “I think that’s a matter for Mr Mackay. I would find it , in those circumstances, very difficult to see how I was actively going to be able to uphold the standards that are expected of politics generally and the reputation of politics generally.”