Police say they are assessing two allegations of electoral fraud, after claims the Tories offered peerages to Brexit Party election candidates to persuade them to stand down.
Labour peer Lord Falconer has urged the Metropolitan Police and prosecution service to launch an investigation.
He said the claims – first raised by the Brexit Party’s Nigel Farage – “raise serious questions” about the integrity of the 12 December election.
The PM says the claims are “nonsense”.
“I am sure there are conversations that take place between politicians of all parties but certainly nobody’s been offered a peerage,” Boris Johnson said on Friday.
The claims came after the the Brexit Party had announced that it would not field candidates in any seats won by the Conservatives in 2017, to avoid splitting the pro-Brexit vote.
But the party said it would contest all other seats, prompting pressure from Conservatives who urged Mr Farage to withdraw more candidates to help Mr Johnson win a majority in Parliament.
In a video posted on Twitter earlier this week, Mr Farage claimed he and eight other Brexit Party figures had been offered jobs “in the (Brexit) negotiating team and in government departments” while there had been “hints at peerages too”.
Ann Widdecombe, a Brexit Party candidate, said she was prepared to swear on the Bible that she had been approached with an offer of “a role” in the next phase of Brexit negotiations.
A Conservative source also told the BBC that the Brexit Party candidate in Peterborough, Mike Greene, had been offered an unpaid role in education in the hope it would convince him to stand aside.
The Brexit Party candidate’s team said Mr Greene would definitely be running in the Cambridgeshire constituency, which Labour held narrowly at a by-election in June.
In a letter, Lord Falconer, the former Labour Lord Chancellor, said he wanted to raise the issue “as a matter of urgency”.
He wrote to Cressida Dick, the Met Police commissioner, and Max Hill, the director of public prosecutions, saying: “I believe these allegations raise serious questions about the integrity of the upcoming general election, and in particular whether senior individuals at CCHQ [Conservative Campaign Headquarters] or No 10 have breached two sections of the Representation of the People Act 1983.”
Lord Falconer added: “These are exceptionally serious allegations which the DPP must, in accordance with his statutory duty, fully investigate as a matter of urgency.
“In addition, in order to maintain public confidence in the integrity of our electoral processes and this election, it is crucial that the Metropolitan Police also examine these accusations.”
In a statement, the Met Police said it “has received two allegations of electoral fraud and malpractice in relation to the 2019 general election.
“The MPS Special Enquiry Team is responsible for investigating all such criminal allegations. Both allegations are currently being assessed.”
The force added that it would not comment on individual cases.
The lord chancellor is a role dating back many centuries, and which also heads up the Ministry of Justice.
Speaking during a question-and-answer session on BBC Radio 5 Live on Friday, Mr Johnson responded to Mr Farage’s comments, saying: “What is this nonsense?
“I am sure there are conversations that take place between politicians of all parties but certainly nobody’s been offered a peerage.”