JULIAN ASSANGE’S fight against extradition to the US is “one of the most important and significant political trials of this generation,” John McDonnell said today when visiting him at Belmarsh Prison.

Speaking at the gates, the shadow chancellor condemned Mr Assange's treatment, who he said is being “persecuted for political reasons, for simply exposing the truth for what went on in relation to recent wars.”

Mr Assange is being held in a cell for 20 hours a day while awaiting the extradition hearing that begins at Woolwich Crown Court on Monday.

On Tuesday it emerged that inmates at Belmarsh successfully lobbied for his release from solitary confinement.

Mr Assange is wanted in the US to face 18 charges, and is accused of working with former US army intelligence analyst Chelsea Manning to leak hundreds of thousands of classified documents.

If found guilty he could be sentenced up to 175 years in prison.

Mr McDonnell added: “I think if this extradition takes place it will damage the democratic standing of our own country as well as [the US’s].

“We have a long tradition in this country of standing up for journalistic freedom, standing up for the protection of whistleblowers and those who expose injustices.”