Police are investigating five allegations of malpractice relating to the Peterborough by-election, which Labour won by 683 votes.
Three of the allegations relate to postal votes, one is of bribery and corruption and the fifth is of a breach of the privacy of the vote, Cambridgeshire Police said.
Labour candidate Lisa Forbes was elected after the by-election on June 6, with Nigel Farage’s Brexit Party in second place.
Peterborough Council said on June 10 that it received one unconfirmed report regarding alleged bribery prior to polling day.
This was referred to police and no further action will be taken, the authority said.
In a statement, the council said that one other concern was received on polling day which was also referred to police, but could not be substantiated.
The council said it had seen no evidence that postal voting fraud had taken place.
Postal votes accounted for 9,898 of the 33,998 ballot papers received, and 400 of the postal votes returned were rejected due to either the signature or date of birth or both not matching council records.
The by-election was called after Peterborough’s previous MP Fiona Onasanya was forced out after she was jailed for lying about a speeding offence.
Onasanya was elected as a Labour MP in 2017 with a wafer-thin majority of 607, but was suspended from the party after she was sentenced.
The by-election saw Labour’s Lisa Forbes win the seat by 683 votes ahead of the Brexit Party’s Mike Greene. However, the Conservative deputy leader of Peterborough City Council, Cllr Wayne Fitzgerald, has alleged there was “harvesting” of postal votes, while the Tories have highlighted the involvement in the campaign of Labour activist Tariq Mahmood who was jailed in 2008 for postal vote interference.
Mr Mahmood was pictured with Ms Forbes during the campaign and was also present at the election count – just as he has been at previous elections.
However, Labour has categorically denied that Mr Mahmood had any involvement in the campaign, with a spokesman saying: “Peterborough council, who organise the count, always announce the results in a public area of the venue. There were hundreds of people there. The Labour Party had 19 official guests who were allowed into the restricted areas. He was not one of them.
Members of the public can of course support Labour, but this individual did not play any role in Labour’s campaign.
In 2008, Tariq Mahmood, now 51, was convicted alongside fellow Labour members Maqbool Hussein and former Peterborough Mayor Mohammed Choudhary for forgery over a devious scheme to fabricate votes for the Peterborough City Council election of June 2004.
The four-month case that saw Mahmood (a Labour Party Secretary) sentenced to a 15-month jail term the estimated trail cost to the taxpayer was a whopping £850,000.
Police have been asked to investigate a claim, made on social media, that an individual burned more than 1,000 votes destined for the Brexit party; and that some voters were observed taking photographs of ballot papers, leading to concerns that they were fulfilling some form of contract.
It is not known if these claims are part of the latest Cambridgeshire police inquiry.
In a statement, the council said that on top of the claims sent to the police, another concern was received on polling day that was also referred to police, but could not be substantiated.
The council said it had seen no evidence postal voting fraud had taken place.
Labour sources have previously said claims that their campaigners have been involved in electoral fraud are a “racist trope”.
The authorities have been keen to stress that so far there has been no evidence of electoral fraud committed, with Peterborough City Council issuing a lengthy statement on its website on Monday after being inundated with queries from members of the public.
Brexit Party candidate Mike Greene finished on 9,801 votes to Forbes’ 10,484, which Conservative candidate Paul Bristow collected 7,243 votes.