Sinn Fein MP for Mid Ulster Martin McGuinness is to resign his seat in the House of Commons, forcing a by-election, as part of a shake-up to end Sinn Fein dual mandates at Westminster.
Party president Gerry Adams said Sinn Fein's four other MPs will stand down from the Northern Ireland Assembly where new representatives can be put in their place without further elections.
Mr Adams said his party would continue to refuse to sit in Westminster, but wanted to avoid creating a string of electoral contests by resigning all five of its parliamentary seats.
Stormont politicians have been heavily criticised in the past for holding posts in local councils, the devolved Stormont Assembly and at Westminster.
The Sinn Fein MPs set to leave the Assembly are West Belfast representative Paul Maskey and West Tyrone representative Pat Doherty, plus former Stormont ministers Fermanagh/South-Tyrone MP Michelle Gildernew and Newry/Armagh MP Conor Murphy.
Mr Adams is a former MP and Assembly member for West Belfast and resigned the seats to successfully contest a parliamentary seat in Louth in the Irish Republic where his party has enjoyed increased support.
"Our party is developing across the island. We have a lot of work to do to meet our potential," he said.
He said of his MPs' future roles: "There will be lots of work to do in terms of both lobbying and policy.
"We will not be taking up seats at Westminster, just to make that clear.
"We also will be putting in place a programme of work across Britain strictly in relation to promoting the merits of Irish unity."