23/07/2015 03:20 BST | Updated 22/07/2016 06:12 BST

Green Party Politicians' Communications 'Intercepted By GCHQ'

Claimsthat the communications of two Green Party politicians are being intercepted by GCHQ will come under scrutiny today.

The Investigatory Powers Tribunal - which considers complaints about the way public authorities use covert techniques - will hear a case brought by Caroline Lucas, MP for Brighton Pavilion, and London Assembly member Baroness Jones of Moulsecoomb.

Lawyers allege their communications are being intercepted as part of the Tempora programme, which monitors and collates on a blanket basis the full range of electronic communications data produced in, or transiting through, the UK and other countries.

The communications it intercepts include emails and other internet traffic as well as telephone calls.

They are set to argue that the surveillance is in breach of the Wilson Doctrine and parliamentary privilege.

The Wilson Doctrine, implemented by Prime Minister Harold Wilson in November 1966, provides that no MP's telephone shall be tapped unless there is a major national emergency, and that any changes to the policy will be reported by the Prime Minister to Parliament.

Rosa Curling from law firm Leigh Day, which also claims the Government acted in breach of Article 8 and Article 10 of the European Convention on Human Rights, said ahead of the two-day contested hearing in London: "It is crucial that parliamentarians are able to have confidential communications with their constituents.

"There must be proper judicial oversight in relation to any surveillance that the intelligence services may wish to undertake of parliamentarians' communications."

Baroness Jones said: "As parliamentarians, our job is to hold ministers to account. If our communications are subject to blanket surveillance, and people are less able to freely contact us with important and sensitive revelations, then our ability to do our job is hugely curtailed.

"There is a clear public interest in protecting the communications of parliamentarians from unnecessary surveillance, which is why we're bringing this case to court to halt any attempt to trample on the Wilson Doctrine."

Ms Lucas said: "The blanket surveillance of the communications of parliamentarians could have a deeply chilling effect on our relationship with the public. Parliamentarians must be a trusted source for whistle blowers and those wishing to challenge the actions of the Government.

"My constituents have a right to know that their communications with me are free from blanket monitoring. It's absolutely vital that the trust between MPs and constituents is maintained – and that people feel able to communicate freely with their representatives in Parliament."

Former MP George Galloway has filed a separate case against the Government, which has been incorporated with that of Ms Lucas and Baroness Jones.