A bid to force a by-election which could unseat North Antrim MP Ian Paisley is about restoring trust in politicians, one of his leading critics said.
The first ever recall petition opened on Wednesday after the senior Democratic Unionist was suspended from the Commons for 30 sitting days over his failure to declare two family holidays paid for by the Sri Lankan Government.
Mr Paisley could become the first MP to lose his seat under legislation introduced by the former coalition government following the Westminster expenses scandal, although the DUP has a massive majority in North Antrim.
Should 10% of the electorate, or 7,543 people, sign the petition, then a by-election will be held and Mr Paisley is currently suspended from the DUP pending a party investigation.
If he loses the backing of Northern Ireland's largest unionist party, his prospects for re-election would be damaged.
Sinn Fein's Stormont Assembly member Philip McGuigan said: "This is an issue of integrity in Government, it is not an orange and green issue.
"This is not even about nationalism versus unionism.
"This is an issue about trust in your politicians that they will do their jobs with integrity."
In March 2014, the senior Democratic Unionist lobbied the Prime Minister against a proposed United Nations resolution to investigate alleged human rights abuses during a civil war on the Indian Ocean island without disclosing his financial benefit.
Mr Paisley has already apologised for what he said was his "unintentional failure" to register the hospitality, which he estimated was worth £50,000.
He has vowed to fight any by-election campaign.
The DUP's 10 pro-Brexit MPs are crucial allies of the Prime Minister's minority Government.
The recall petition will be open for signing for six weeks.
Nationalist Social Democratic and Labour Party (SDLP) politician Declan O'Loan said he was the first person to sign the petition, in Ballymena in Co Antrim, which has been dominated by Paisleyism for generations.
Mr Paisley has been MP for the constituency since 2010, following in the footsteps of his father and DUP founder Ian Paisley.
The petition can be signed at centres in Ballymena, Ballymoney and Ballycastle.
The Electoral Office is running the petition process and those signing have to produce a driving licence, UK or Irish passport, electoral identity card or bus or rail pass.