ALEX Salmond has been dragged ever closer to the row over alleged sexist language at Westminster, with one of his closest aides accused of stoking up the controversy.

MSP Joan McAlpine became involved after her researcher was revealed to be seeking to create a public demonstration after Scottish Affairs Select Committee chairman Ian Davidson was alleged to have threatened that one of its members, SNP MP Dr Eilidh Whiteford, would get “a doing” if details of a private discussion were leaked to the media.

An email from Ms McAlpine’s assistant, Gail Lythgoe, which was made public by Labour, acknowledged that party involvement had to be downplayed, prompting a claim that dirty tricks were being waged against Mr Davidson.

He has strenuously denied the allegation that he threatened Ms Whiteford and claimed every other MP present backed his version of events.

There were no protests outside Glasgow City Chambers as Mr Davidson turned up yesterday for its latest meeting following Ms Whiteford’s resignation over the allegations last week.

During a break between evidence on the Crown Estate and an immigration issue, Mr Davidson, the MP for Glasgow South West, told The Herald: “I am immensely disappointed that Dr Whiteford would allow herself to be used in such a partisan and unfair way.

“I would hope the SNP would recognise that smears and personal attacks are not the best way to conduct politics in Scotland even when there are strong reasons to disagree.”

A Labour Party spokesman said: “This leaked email is a smoking gun and utterly reprehensible. It contains the most vile, false smear and shows the extent to which the dirty tricks campaign against Ian Davidson is orchestrated by the highest levels of the SNP.

“Alex Salmond must apologise for these dirty tricks today and order and independent inquiry into the ethics, practices and management of the SNP student wing because either the party has lost control of its activists and researchers , or their smears are being condoned at the highest level.”

An SNP spokesman said: “This is not an issue of party politics and we hope people of all parties and across civic society will take the opportunity to respond positively to the concerns raise by Dr Whiteford, in particular the budget group’s call for Scotland’s political future to be marked by a commitment to equality.”

There was a fresh attack on Mr Davidson yesterday from the same academic group that wrote to The Herald two days ago.