Sinn Fein and the SDLP have pledged to support a bid to unseat Ian Paisley in North Antrim, after the DUP MP was suspended by both Parliament and his party.
However, unionist parties have said they will not be actively involved in any campaign to oust Mr Paisley.
The 30-day sanction imposed by the House of Commons will force a by-election if 10% of North Antrim voters – about 7,600 people – sign what is known as a recall petition, the first of its kind in UK Parliamentary history.
A public process that will see up to 10 venues opened in the constituencey to collect signatures over a six-week period is expected to be triggered in the coming days.
Yesterday, the SDLP said it would be taking action to ensure the requisite number of signatures are obtained to force Mr Paisley to resign.
A party spokesperson told the News Letter: “The SDLP cannot and will not accept a situation whereby elected representatives are above the rules set to ensure transparency and accountability.
“Therefore, in the interests of upholding political integrity the DUP must remove Ian Paisley Jr from the party.
“If party officers fail to do so, then the SDLP will campaign to get the signatures needed to unseat him.”
On Tuesday, Sinn Fein reportedly told the Irish News: “In the coming days we’ll be supporting the effort to oust Ian Paisley from his seat though we believe the onus to act should be on the DUP.”
When asked by the News Letter to elaborate on this yesterday, the party would not clarify whether it intends to act as a campaigner during the petition.
There are a host of regulations pertaining to the recall petition, including spending limits for campaigners and rules regarding donations.
According to the Electoral Commission guidance, there is a £500 spending limit for unregistered campaigners during the petition period, while registered campaigners have a cap of £10,000.
The UUP confirmed it will not be a registered campaigner, but a spokesperson added that party leader Robin Swann would be signing the petition.
“We would encourage North Antrim electors who think what Ian did was wrong, to sign and allow the entire North Antrim electorate to have their say,” the party said.
TUV leader Jim Allister, a former ally and friend of Ian Paisley’s father, also said his party would not be involved in formal campaigning during the petition.
He added: “The law must take its course and that will afford every constituent the opportunity to make up their own mind. It is not something I intend on taking a party line on.
“My own view is that Mr Paisley has behaved in a manner unworthy of an MP and therefore the logic of that is that he shouldn’t be one.”
Mr Paisley was suspended from the Commons for failing to declare two lavish family holidays paid for the Sri Lankan government, and then lobbying on behalf of the controversial regime.
The DUP has also suspended Mr Paisley while it carries out “further investigation into his conduct”.
Mr Paisley has vowed to fight any by-election, where he will be defending a majority of more than 20,000.