Scottish Conservative MP John Lamont has written to Mr Blackford demanding answers to why a claim made by an SNP staffer about Mr Grady had not previously been investigated and urged him to suspend the MP from the SNP.
The Berwickshire, Roxburgh and Selkirk MP said Mr Blackford should also reveal to what extent he – and his predecessor Angus Robertson – were aware of concerns about Mr Grady’s behaviour, as well as that of another unnamed SNP MP, prior to the complainer going to the media with his accusations.
Mr Lamont said Mr Blackford should “commit to immediately suspending both Patrick Grady and the other as-yet-unnamed SNP MP from the SNP, subject to investigation ... including from any spokesperson role that the as-yet
unnamed MP may have” as well as lay out the steps he is taking “to combat sexual harassment in the SNP MP group”.
He also said claims complainers were “too scared” to come forward because Mr Grady was being “protected” must be “urgently and honestly” investigated.
Mr Lamont said: "The SNP's Westminster leader Ian Blackford and other senior figures have some serious explaining to do.
"We now know that party employees raised concerns about the chief whip's alleged sexual misconduct as long ago as 2017 — yet nothing appears to have been done.
"The suggestion that Grady was ‘protected’ by the party is chilling and must be urgently and honestly investigated – not the usual SNP cover-up.
"This appears to go to the very top. If Blackford knew and did not act, what about Nicola Sturgeon and Peter Murrell?"
Mr Lamont’s letter to Mr Blackford comes a day after Nicola Sturgeon revealed she was aware of “concerns” about Mr Grady before a formal sexual harassment complaint was made against him.
The Glasgow North MP stood aside from his Westminster role following claims he groped two male researchers at an SNP Christmas party in 2016. Further allegations have also emerged about claims that Mr Grady, 41, “inappropriately” touched an SNP staff member, then aged 19, in a London pub.
In his letter, Mr Lamont said what was most concerning about the revelations was that Mr Grady had “for a significant period of time, allegedly been protected by the SNP due to his status within the party”.
He writes: “Particularly damning is the quote, taken from one of the letters sent to the Speaker in late 2017 and early 2018, that states ‘given the position of Patrick Grady as chief whip, staff are scared to come forward because he is protected by the party’.
“Equally concerning is the claim, made in a further letter, that Mr Grady’s misconduct was widely known about within the SNP group, yet action was not being taken against him and his behaviour was effectively being supported by his SNP colleagues.
"These concerns are, of course, only amplified by your party leader Nicola Sturgeon confirming this week that she was aware of concerns about Grady’s behaviour before any formal complaints were made about him.”
An SNP spokesperson said: "The SNP has followed due process and taken appropriate action at every stage. The SNP national secretary has now had a formal complaint notified to him and will investigate accordingly."But we will take no lectures from the Conservative Party, who have a frankly appalling record when it comes to handling complaints – such as the decision to readmit two suspended MPs ahead of a vote of no confidence in Theresa May, refusing to suspend an MP arrested on suspicion of rape, and hushing up an investigation into a senior MSP until he was cleared in a process heavily criticised by Rape Crisis Scotland."