The 61-year-old, who is Northern Ireland's longest-serving MP, was suspended by the party following his arrest last month.

In a statement at the time, the DUP said: "The Party Chairman has received a letter from Sir Jeffrey Donaldson MP confirming that he has been charged with allegations of an historical nature and indicating that he is stepping down as Leader of the Democratic Unionist Party with immediate effect.

"In accordance with the Party Rules, the Party Officers have suspended Mr Donaldson from membership, pending the outcome of a judicial process."

In his resignation letter, he said he would be strenuously contesting the charges.

Sir Jeffrey Donaldson had been arrested at his home in County Down the previous morning and taken to Antrim Police Station for questioning.

In a short statement, the Police Service of Northern Ireland confirmed that a 61-year-old man had been charged with "non-recent sexual offences" and that a 57-year-old woman, arrested at the same time, had been charged with "aiding and abetting" in connection with the offences.

Both are due to appear before Newry Magistrates Court in County Down.

Sir Jeffrey Donaldson, who has been MP for Lagan Valley for 27 years, was knighted for his services to politics in 2016.

He helped broker the DUP's £1bn confidence and supply deal with Theresa May's minority Tory government, when the party held the balance of power at Westminster between 2017 and 2019.

More recently, he had compromised and led his party back into the power-sharing government at Stormont, which it had boycotted for two years over post-Brexit trading arrangements.