The Scottish Conservatives are refusing to comment after fresh allegations emerged about the behaviour of MP Ross Thomson.
The Daily Record says a male Scottish MP experienced "unwanted physical touching" from Mr Thomson last year.
The MP - who has not been named - has now made an official complaint to parliamentary authorities.
Mr Thomson is already being investigated by the party over complaints about his conduct in a bar.
A source close to the Aberdeen South MP said it would be "inappropriate" to comment at this time, but he has strongly denied any wrong-doing.
The Daily Record has reported that the MP who made the latest allegations about Mr Thomson has claimed that he experienced unwanted physical contact from the Tory MP in the Strangers' Bar at the House of Commons at the end of last year.
He is said to have now made an official statement to the parliament's sexual harassment hotline, and to have been in contact with Westminster's Parliamentary Standards Commission.
The MP was frustrated at what he saw as Mr Thomson's denials about his behaviour.
In a separate incident on 5 February, police were called to the same bar and spoke to Mr Thomson about allegations of "sexual touching".
No arrests or complaints were made at the time of the incident.
The allegations about the MP's behaviour in the bar in the February incident were later described as "completely unacceptable" by interim Scottish Conservative leader Jackson Carlaw.
But Mr Thomson said the allegations were "completely false", and referred himself to the Conservative Party's disciplinary panel.