A 56-year-old man was jailed on Thursday for three years for threatening to kill the former Labour Party leader Ed Miliband earlier this year.

On March 22 Michael Donaldson accosted Miliband and two members of his staff in Doncaster and said “Oh you're Ed Miliband, I am going to slit your throat, I am going to slit your f****** throat, I am going to do it now.”

Miliband and his staff were forced to take refuge in a nearby building and were left shaken by the incident.

Donaldson was arrested on the day the incident took place, telling police he had drunk about one litre of vodka and later trying to claim that the incident was just a “joke”.

In May he pleaded guilty to one count of making threats to kill.

Judge Jeremy Richardson KC, who sentenced Donaldson at Sheffield Crown Court on Thursday told him, according to media reports: “To make a threat to kill an MP is not only a serious matter for that individual, it is a form of attack on parliamentary democracy in this country.

“It undermines the rights of the public to have access to their MP because of the enhanced necessity for security.”

The judge added: “An attack of the kind you perpetrated had nothing to do with legitimate political discourse or political criticism, it was a serious crime and you must be punished for it."

Shaun Sigamoney, of the Crown Prosecution Service, said: “Michael Donaldson threatened Mr Miliband, despite his effort to play down the incident as a joke or drunken foolishness.

“His actions have no place in a civilised society. Neither Mr Miliband nor his members of staff should have been subjected to such vitriol – it is completely unacceptable.

“Members of Parliament play a vital role in our democracy – those who engage in this criminal behaviour will face the consequences of their actions.”

Ed Miliband, who led the Labour Party between 2010-2015, currently serves as Secretary of State for Energy Security and Net Zero in Sir Keir Starmer’s government.