The disgraced former MP Keith Vaz has made a surprise bid to re-enter Labour politics after being declared as the chair of the constituency party that he represented for 32 years, the Guardian can disclose.

The former minister, who did not stand for parliament at the last election after receiving a six-month Commons ban over drug allegations involving sex workers, was voted in as chair of Leicester East Labour party on Tuesday night.

Amid angry scenes, police attended the meeting in Belgrave Neighbourhood Centre. They have since confirmed that they have been asked to investigate an allegation of assault.

Inside the meeting, Vaz was voted in as the new chair on a show of hands. While his supporters said he had re-entered politics because the local party was in chaos, other local party members said the meeting involving more than 100 people should not have taken place and that his election should be declared void.

There is no implication that Vaz has personally broken any party rules.

John Thomas, the former chair of Leicester East Labour party and an ally of Vaz, said Vaz had stood because the local party was failing to function. “The local party is in absolute chaos. Some people have demanded that Keith get involved,” he said.

There was disquiet among some members because the constituency’s new MP, Claudia Webbe, was leftwing, he said. “The new MP is a Corbyn supporter but the party in Leicester is much more to the right. Keith knows the people here.”

One Vaz opponent said it was widely rumoured that the former MP would like to stand again at the next election, and his position as chair would give him a platform for this. “He wants to get back to Westminster. That is the rumour and now he is perfectly positioned,” the source said.

Webbe was voted in with a much-reduced majority in December. Vaz pointedly did not campaign with her during the election.

Vaz, once the UK’s longest-sitting MP of Asian origin, was given the longest ban ever received by an MP for offering to buy cocaine for sex workers and obstructing inquiries by the standards commissioner.

A parliamentary inquiry examined claims published in the Sunday Mirror in 2016 that he offered to buy cocaine for male sex workers while posing as an industrial washing machine salesman called Jim. At the time, Vaz was chair of the home affairs select committee, which was examining the issues of drug use and prostitution.

Vaz’s explanation, which included that he had amnesia and could not recall key events, was “not believable and, indeed, ludicrous”, the inquiry found.

Despite facing the longest ban ever imposed by parliament last year, Vaz is also a member of Labour’s ruling body, the national executive committee.

A female party member, who asked not to be named, said she was assaulted as she tried to enter the meeting. Leicestershire police confirmed that the force had received an allegation of assault from Tuesday night’s event. “Further inquiries are being carried out into the allegation to establish whether any criminal offences have occurred,” a spokesperson said.

Andrew Bridgen, the Tory MP for North West Leicestershire, said: “Vaz has been a malign influence upon UK politics for too long and it’s deeply disappointing that he is still seen as a credible representative of the party in Leicester.”

Vaz and Labour have been approached for comment.