According to a report in the Daily Record, the man, who has remained anonymous, was firstly harassed by a male MP and then at a later date by a female MP.
He has also accused SNP Wesminster leader Ian Blackford of an “ambush” when he was asked to his office to discuss the first incident only to find the male MP involved already there.
The SNP has said the man’s account of this meeting is “highly inaccurate” and that it had provided the staff member with “information on the appropriate ways to raise a complaint and offers of support".
The revelation comes after months of turmoil for the SNP as a result of the fall-out of the Scottish Government’s handling of sexual misconduct allegations against former first minister Alex Salmond, and the criminal trial that saw the internal procedures of the party thrust into the spotlight and questions about whether they were fit for purpose.
Mr Salmond was cleared of all charges against him.
First Minister Nicola Sturgeon is believed to have been made aware of the latest complaints.
However, the report claims the SNP staffer believes his allegations have been “happily swept this under the carpet” by the party.
He has claimed the first alleged incident involved a male MP in The Water Poet pub in 2016, when the MP “perched himself on the side of the couch … started putting his fingers down the back of my collar, touching me inappropriately there – he was also grabbing my hair”.
He said he did not take the matter further, but someone else had alerted Mr Blackford. “He calls me into the office and the other MP is sitting on the couch, crying,” he said. The MP allegedly apologised.
“I wouldn’t view this as mediation – I would view it as ambush,” he said.
The complainer said the separate incident, involving a female MP saying “inappropriate things”, happened in January last year in the Strangers Bar in Westminster when the politician was “clearly very, very drunk”.
"She was grabbing my hand, pulling me closer and saying to me things like ‘you should come home with me’.”
The staffer complained to the SNP last month, but as he is not a party member, party governance officer Ian McCann emailed a response that said: “I have to be clear that the national secretary can’t look at a complaint in the context of sexual harassment in the workplace.
"Under the terms of the code of conduct, it would have to be examined solely as sexual harassment by one member against another member.
“If you wanted to make a complaint of sexual harassment within the parliamentary estate, that can only be investigated and dealt with under the terms of the independent scheme provided by Westminster.”
An SNP spokesperson said: "The individual has been provided information on the appropriate ways to raise a complaint and offers of support.
"The picture painted of the meeting in Ian Blackford’s office is highly inaccurate. That’s why it is essential for everyone involved that due process is followed.
"Advice has been offered on how to make a formal complaint so that a proper investigation can be carried out.”