Police are investigating suspected drug offences after allegations were made against the former chair of the influential home affairs select committee, Keith Vaz, who is known for his campaign for the Sri Lankan Tamil force, the Guardian reported.

A Sunday Mirror article on 4 September this year said he had paid male escorts and had been secretly recorded offering to pay for cocaine if it was brought to a future meeting, though he stressed that he did not want any himself.

He was also accused of encouraging others to use poppers. The select committee he formerly chaired has criticised moves to ban the legal high and has investigated prostitution, leading to accusations of a conflict of interest.

After the article was published, Vaz apologised to his family for his actions but attacked the paper for the way it had gone about getting the story. He stepped down from his home affairs select committee position two days after the news emerged.

Police said they received a letter the next day – 7 September – asking them to investigate. The correspondence was passed on to a specialist team, which “started an assessment process to identify what criminal offences – if any – may have been committed”.

On Friday night Scotland Yard said: “Following that assessment, which included obtaining early investigative advice from the Crown Prosecution Service, the Metropolitan police service is now investigating offences under the Misuse of Drugs Act 1971. The investigation started on Thursday 10 November.”

Police confirmed the investigation was launched following allegations against an MP in the 4 September edition of the Sunday Mirror but refused to identify any of the objectives of the investigation and declined to comment further.

On Friday Vaz said: “I welcome a full investigation as a means of establishing the true facts and I am confident the police will pursue all lines of enquiry. I will cooperate with the investigation in any way I can.”

It was announced at the end of last month that Vaz had been appointed to the justice committee, despite opposition in parliament.

Conservative MP Andrew Bridgen told the Commons: “I would leave the house with this question: If the right honourable member for Leicester East [Vaz] found himself last month to be not fit to be chair of the home affairs select committee and the matters are unresolved, what makes him think that he is a fit and proper person this month?”