SCOTTISH Labour are gunning for Nicola Sturgeon over the Derek Mackay affair. Richard Leonard has written to the First Minister demanding to know why she didn’t sack the disgraced former finance minister but instead let him hand in his notice.

Mackay resigned last week following reports he had bombarded a 16-year-old schoolboy with 270 predatory messages.

In the messages, Mackay is reported to have called the boy “cute”.

A number of young men have since come forward to say that they too received inappropriate or creepy messages from the man once tipped to be the next First Minister.

Yesterday, one of Mackay’s former colleagues said he thought it was unlikely the MSP for Renfrewshire North and West could ever return to Holyrood.

READ MORE: WATCH: Nicola Sturgeon's statement to Holyrood on Derek Mackay

In his letter, Leonard has demanded that the SNP leader make public any phone records and notes of any conversation she had with Mackay after learning about his behaviour.

The National: Richard Leonard

The Scottish Government was first informed by the media of the investigations at 5.50pm, on Wednesday. Mackay’s resignation was announced at 8am the next morning, with Sturgeon revealing that he had been suspended from the SNP in a brief statement before First Minister’s Questions at noon.

Leonard also asks Sturgeon if it's true she had previously instructed Mackay “not to drink at SNP conference, thus suggesting he has previously demonstrated inappropriate behaviour.”

READ MORE: Robertson condemns the ‘unacceptable’ actions of Derek Mackay

Leonard said it was “deeply concerning that such a senior member of this parliament was not immediately dismissed” by the First Minister.

The Labour leader added: “The fact that his behaviour was directed towards a teenage schoolboy should have been enough for the First Minister to take decisive and fast action.”

He insisted: “It is now vital that the full circumstances leading to Derek Mackay’s resignation are revealed publicly. The contact Nicola Sturgeon had with Mr Mackay after she was made aware of the allegations should be shared immediately.”

A spokesman for the First Minister said: “Both the Scottish Government and SNP acted swiftly, decisively and entirely appropriately when the details of this issue came to light. Derek Mackay is no longer a minister, and he is suspended from both the SNP and the parliamentary group pending an investigation by the party.”

Meanwhile, Keith Brown said Holyrood rules meant any decision to quit as an MSP could only come from Mackay.

READ MORE: No criminal complaints filed against Derek Mackay, Police Scotland say

Speaking on the BBC’s Sunday Politics Scotland programme, he said it was an extremely serious situation for the boy and that it was being treated “very seriously”.

He added: “As for Derek Mackay’s own future, that’s something that only he can decide. It is not something over which the SNP or the Government have any control.

“As things stand Derek Mackay is a suspended member of the SNP and there will be a process through which we will have to go and I think it’s better that I don’t comment on that just now.”

But the deputy leader added that he found it “very difficult” to see how Mackay could continue in his role as MSP. Brown also backed Kate Forbes – who stepped in at the last minute to cover for Mackay to deliver the Scottish Government’s budget – to become the country’s next finance minister. However, he added, that would ultimately be a decision for the First Minister.