Martin McGuinness is to resign his seat as the Sinn Fein MP for Mid Ulster in Westminster, to enable a party shake-up.
Sinn Fein president Gerry Adams confirmed the parties four other MPs will also step down from the Northern Ireland Assembly, as the party seeks to bring an end to double jobbing.
He said: “The key thing to be said about this issue is that other parties are talking about ending dual mandate, Sinn Féin has ended dual mandate.”
“Our party is developing across the island. We have a lot of work to do to meet our potential,” he added.
“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.”
"Martin will resign as MP for Mid Ulster to concentrate on his work in the assembly and as deputy first minister. This will obviously necessitate a byelection for Westminster," Adams said.
McGuinness who has held the seat since 1997, thanked everyone who had voted for him in the past.
“I want to take this opportunity to thank all of those people who supported me for the last 15 years in election after election,” McGuinness said.
The Deputy first minister of Northern Ireland will now focus all her attention on his work at Stormont.
“I am in a different position from my colleagues, in that I will be continuing on as an MLA,” he said.
“But my work on their behalf will continue in this Assembly.”