AN East Renfrewshire politician has suggested the reputation of the Scottish Parliament could be damaged unless disgraced MSP Derek Mackay stands down.

Jackson Carlaw made the comments at Holyrood today after former finance secretary Mr Mackay was suspended from the SNP following reports he sent hundreds of messages to a 16-year-old boy.

During First Minister's Questions, Nicola Sturgeon faced calls to investigate Mr Mackay's "predatory" behaviour after the Renfrewshire North and West MSP stepped down from his Cabinet post.

There have been calls for Mr Mackay to also quit as a MSP.

Ms Sturgeon said his conduct "falls seriously below the standard required of a minister" and he had been suspended from both the party and the SNP parliamentary group at Holyrood "pending further investigation."

The father-of-two, who came out as gay in 2013, quit as finance secretary after The Scottish Sun reported he sent 270 messages to a boy he befriended on Facebook and Instagram.

Mr Mackay has accepted he had "behaved foolishly" as he apologised unreservedly to the youngster and his family.

In one message, he is alleged to have asked the teenager: "And our chats are between us?"

When the boy agreed, Mr Mackay told him: "Cool, then to be honest I think you are really cute."

The newspaper alleges he contacted the teenager over a six-month period and offered to take him to a rugby game and out to dinner.

Eastwood MSP Mr Carlaw, who is interim leader of the Scottish Conservatives, asked Ms Sturgeon if the reputation of the Scottish Parliament could survive while Mr Mackay remained a member.

He also read aloud the definition of grooming, as detailed by the NSPCC children's charity, before asking the First Minister if she believed Mr Mackay's behaviour could be considered as such.

Mr Carlaw asked: "How difficult is it to reconcile (Mr Mackay's) conduct with the very worst connotation?"

The First Minister, who had earlier stated there are "matters that Derek Mackay will be reflecting on and will continue to have to reflect on," responded: "I'm not sure if Jackson Carlaw has been paying close attention to my answers.

"I am in no way minimising the seriousness of what we are discussing today."

Scottish Liberal Democrat leader Willie Rennie said Mr Mackay should step down as MSP for Renfrewshire North and West.

He added: "It is really about the standards that we would expect from MSPs at this time and I think Derek Mackay has not behaved in the standard that we would expect from a member of the Scottish Parliament.

"I think it would be time for him to resign now."

Mr Mackay said he takes "full responsibility" for his actions.

He added: "I have behaved foolishly and I am truly sorry.

"I apologise unreservedly to the individual involved and his family.

"I spoke last night with the First Minister and tendered my resignation with immediate effect.

"Serving in Government has been a huge privilege and I am sorry to have let colleagues and supporters down."