Reports of "sexual touching" by Conservative MP Ross Thomson have been referred to Westminster's standards commissioner in a step that could lead to him being sacked.

The complaint against Thomson, MP for Aberdeen South, has been made by a Westminster researcher who was part of a group having a drink in the Strangers' Bar in the House of Commons on Tuesday night.

Thomson was led away from the bar and spoken to by police after reports of "sexual touching".

In a statement released on Friday he firmly denied the claims and referred himself to a Tory disciplinary panel.

Three men, including the 31-year-old MP, were said to have been involved in the incident before officers were alerted at around 11pm on Tuesday.

The Metropolitan Police said no one was arrested and no formal allegations were made.

On Friday, after Thomson's denial, Catriona Matheson, the SNP's head of communications at Westminster, described his statement as "jaw-dropping".

She tweeted: "It was the talk of parliament because the bar was packed and there were multiple eye-witnesses. I spoke to several people who were horrified by what they saw."

The complaint will be dealt with by Kathryn Stone, the commissioner for standards, who has authority to investigate complaints about harassment and sexual harassment.

Ms Stone has the power to trigger sanctions including suspensions, calling for an apology or insisting on compulsory training for the member involved.

However, if a complaint is particularly serious it can be passed to the committee of standards who can vote on more serious breaches, including sacking.