Jackson Carlaw read out the definition of grooming in parliament amid the fallout of the .
The Scottish Tory interim leader referred to child abuse charity NSPCC's interpretation while putting questions to First Minister in the Scottish Parliament.
The site makes reference to an “authority figure” using “social media networks and text messaging” to “give attention” to young people by taking them "on trips, outings or holidays".
His comments came after the SNP leader confirmed in Holyrood that her former finance secretary had stepped down amid claims he was messaging a 16-year-old boy.
The Scottish Sun reported that the 42-year-old MSP for Renfrewshire North and West sent a series of messages to the teen on social media.
In the online messages, it is alleged he invited the boy to dinner and to attend a rugby event, as well as calling him "cute".
Mackay was due to present the Scottish government's budget at Holyrood later, with Public Finance Minister Kate Forbes now stepping in.
Carlaw followed up reading the definition in parliament by asking how hard it is to reconcile Mackay’s conduct with “the very worst connotation”.
Posting a screenshot of the NSPCC's website, he tweeted: "This is the definition of grooming from the NSPCC. Derek McKay's behaviour is completely unacceptable and I believe he has no option other than to resign as an MSP.
"Nicola Sturgeon should show clear leadership and join those calling for him to go."
He was not the only Scottish leader to demand Mackay be removed as an MSP with Scottish Labour leader Richard Leonard branding the suspended politician "predatory".
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."
In her address, Sturgeon revealed she does not know the boy at the centre of the allegations and said she has no knowledge of any other allegations.
Her comments came after confirming Mackay's suspension from the SNP, saying he is 'no longer a member of her government'.
Sturgeon said: "This morning I have read the full transcript in the Sun and it is on that basis he has been suspended.
"If the family or the individual wanted to speak to me I would of course be happy to do that.
"It was unacceptable and falls seriously below the standard required of a minister."
In a statement made earlier today, Mackay 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. I spoke last night to 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."
