Nigel Farage has vowed to stand candidates against Tory MPs who vote against Prime Minister Boris Johnson's Internal Market Bill.
In a tweet on Monday, Farage warned: "MPs who vote for Brexit in name only will see campaigns launched against them in their seats."
"The withdrawal agreement as it stands is not the Brexit we fought for," he wrote, adding that "Boris misled us but is now trying to make amends" through the bill that amends the Northern Ireland Protocol in last year's European Union (EU) Withdrawal Agreement.
Farage told website Guido Fawkes: “The Brexit Party still has a large and engaged database. We could fire up ground campaigns against these MPs very quickly”.
But only 15 have publicly stated their opposition to the legislation, and even 30 MPs voting with the opposition would not be enough to overturn the government majority of 80. Furthermore, Northern Ireland's Democratic Unionist Party, with eight MPs in Westminster, could support the bill with amendments to take it even further.
On Sunday, Irish Foreign Affairs Minister Simon Coveney denied reports the EU would impose a blockade on food supplies to Northern Ireland if Parliament votes for the bill, as Johnson claimed on Saturday, by refusing to list it as a "third country" for trade purposes.
But Coveney, who is also Ireland's defence minister, told the BBC's Andrew Marr programme that there would be "limited checks" at the land border between the Republic of Ireland and Northern Ireland to prevent goods produced in England, Scotland and Wales being brought into the EU without paying tariffs.
As leader of the UK Independence Party (UKIP), Farage led the Leave campaign in the 2016 EU membership referendum to victory, forcing the resignation of pro-Remain Conservative PM David Cameron.
The Brexit Party which Farage co-founded in early 2019 came first in that year's European Parliament elections, which forced Cameron's successor Theresa May, who had pushed for a 'soft Brexit', from office.
But neither party has ever had great success in Parliamentary elections.