Martin McGuinness has been awarded an English aristocratic title to secure his resignation as an MP, the Treasury confirmed.
The Sinn Fein politician, who has never taken his seat in Westminster, was appointed Steward and Bailiff of the Manor of Northstead – one of two posts which allow MPs to formally leave the Commons.
In a statement, the Treasury said: "The Chancellor of the Exchequer has this day appointed James Martin Pacelli McGuinness to be Steward and Bailiff of the Manor of Northstead."
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The job has no actual responsibilities and is unpaid. However, parliamentary protocol dictates the only way to resign as an MP is to accept an office of profit under the Crown.
Sinn Fein president Gerry Adams had a similar title conferred on him after his resignation as MP for West Belfast, but he branded the system antiquated and bizarre.
A spokesman for Sinn Fein said: "Martin McGuinness resigned the same way as Gerry Adams in 2011. As Irish republicans we gave no time for antiquated titles of the British parliamentary system then and this remains the situation.
"What we need to see now is the writ being moved for a by-election to allow the people of Mid-Ulster to have their say."
Mr McGuinness, who was elected as MP for Mid Ulster in 1997, said his decision to stand down was in line with Sinn Fein's commitment to end double-jobbing and to concentrate on his role as Stormont MLA and Deputy First Minister.
Francie Molloy will run for the seat in his place.