Brexit Party leader Nigel Farage has claimed the Conservatives offered his candidates jobs and peerages to try to get them to stand down.
Mr Farage also said his candidates received "thousands of phone calls and emails" trying to get them to withdraw ahead of next month's election.
He made the claims shortly after candidate nominations closed before the 12 December poll.
The Tories denied offering Brexit Party candidates jobs or peerages.
Mr Farage has confirmed his candidates will not contest seats won by the Tories at the 2017 general election, but will stand candidates against the party elsewhere.
Conservative figures have urged his party not to run in Labour-held marginal constituencies, fearing his candidates could divide the Brexit-backing vote.
In a video posted on Twitter, Mr Farage said that he, along with eight "senior figures" in his party, had been offered peerages to stand down.
He said the offer had been made by people "deep inside Number 10 Downing Street" - although he did not think Prime Minister Boris Johnson was involved.
"As you can imagine, I said I do not want, and I will never have, anything to do with this kind of behaviour," he said.
A Tory source has told the BBC the Brexit Party candidate in Peterborough was offered an unpaid role in education in the hope it would convince him to stand aside.
Mike Greene is standing for the party in the Cambridgeshire constituency, which Labour held narrowly at a by-election in June.
It is understood friends of Mr Greene had indicated that the role could be enough of an inducement.
Mr Greene's team confirmed the offer of a role had been made to him, but said their candidate would definitely be running.
'Calls, emails and threats'
Mr Farage also later said his candidates had been "subjected to thousands of phone calls, and emails and threats all over the country" to get them to stand aside.
He said candidates had been offered jobs "in the negotiating team, jobs in government departments and hints at peerages too".
A spokesperson for the Conservative Party said: "We don't do electoral pacts - our pact is with the British people."
"The only way to get Brexit done and unleash Britain's potential is to vote for your local Conservative candidate".
Speaking on BBC Question Time, Conservative party chairman James Cleverly said allegations that his party has offered peerages were "completely unfounded".
"There are a number of people who went to the Brexit Party, who had been up until very, very recently Conservatives," he said.
"I have no doubt that Conservatives will have spoken to people they know locally and said 'if you genuinely want to deliver Brexit, the only way of doing that is with a Conservative majority government'.
"I have no doubt conversations like that have been happening up and down the country."
But he added: "I'm telling you that I have no truck with a pact or agreements. Nigel Farage has asked for one for months. We said no."
Labour party chairman Ian Lavery said: "It looks like Boris Johnson is trying to stitch-up this election by offering jobs to Brexit party candidates to get them to stand down.
"This gives a whiff of the corrupt way the establishment works. We can't allow the Tories to run the country a minute longer. It's time for real change."
Liberal Democrat deputy leader Ed Davey said the Conservative Party had seen a "hard-right takeover" that "has now been endorsed by both Trump and Farage".
"As Nigel Farage has admitted, the Liberal Democrats are the only party at this election that can take seats from the Conservatives, stop Brexit and build a brighter future," he added.