Williamson spoke to Sputnik at the scene of a second day of protests outside London's Belmarsh Prison, which currently houses Assange.
"It's appalling, frankly, the way in which he's been treated and I'm really disappointed in the Ecuadorian authorities for removing the asylum… Julian Assange is somebody who has done a lot to shine a light on real abuses of state power and the war crimes that we saw in Iraq, so it's really key, I think, to ensure that we give the public the information so that we can hopefully ensure that politicians, at least in this country, don't ever take us into an illegal war again as we saw in Iraq in 2003," Williamson said.
Williamson added it was "vitally important" that pressure be applied to the UK government to ensure Assange was not delivered into US custody, claiming his previous work was necessary in terms of helping the public hold the government to account.
"It's really important that we demonstrate our solidarity with Julian Assange… I think the key thing is we try and build public pressure on the government and the authorities here to ensure that Julian Assange is not extradited. That's absolutely vitally important," he argued.
Joined by political commentator and former lawmaker from the UK Independent Party, George Galloway, both politicians raised a call for Assange's immediate release, claiming he had an abundance of support from proponents of free speech across the globe.
Although Swedish authorities abandoned their case against Assange in 2017, supporters of WikiLeaks have long feared his possible extradition could ultimately involve his relocation to the United States, where he remains wanted over his role in the leaking of classified military and diplomatic cables from 2010 onward.
One particularly controversial piece, consisting of gun camera footage leaked to Assange's organization by former US army soldier Chelsea Manning, appears to show US Apache gunships firing on civilians in Iraq in 2007.
Dubbed "Collateral Murder," the footage prompted worldwide concern over the conduct of US forces stationed in the Middle East, something supporters of WikiLeaks argue remains behind Washington's renewed drive to extradite Assange to face charges in the United States.