Conservative Party chairman James Cleverly has dismissed as a “gimmick” an attempt from the Liberal Democrats and the Scottish National Party to trigger a 9 December election.
He said the government – which wants a poll three days later on 12 December – had put forward its plan first.
But Lib Dem Jo Swinson said their plan removes the threat of no-deal through a Brexit extension to 31 January.
She said the bill would enshrine their proposed election date into law.
The Lib Dems and SNP have said they reject the government’s election date, which they believe would include time for the PM to “ram through” his Brexit Bill.
The prime minister has said if MPs support a vote on Monday in the Commons for an election on 12 December, he will use the remaining time before Parliament is dissolved on 6 November to try to pass the legislation for his Brexit deal.