'We're being bugged!' Anti-Chequers deal Brexiteers fear security services are monitoring calls and meetings

Senior Brexiteers working to stop Theresa May's Chequers deal have started to take precautions amid concerns that the British security services are snooping on them.

Eurosceptics have started to hold important meetings face to face and to commit as little as possible to email because of the concerns that spies  might be listening in on them.

The concerns are particularly shared by campaigners, MPs and even Eurosceptic ex-ministers because of their commitment to fighting the Chequers deal.

One Brexit source said they had found that their mobile phone calls regularly dropped off, clicks were heard on the line or scrambled noises were heard.

The source said: “We have great difficulties talking to each other on the phone. It is beyond bizarre the stuff that happens. We 100 per cent take precautions, as many precautions as we can.”

Another source said that at least one senior Brexiteer “did not discuss anything that sensitive over the telephone” when they were in Government.

Brexiteer MPs have discussed in private whether their conversations are being bugged, another source confirmed, although they had tried to brush off the concerns.

The claims were dismissed by a Government security source who said the Brexiteers were "paranoid".

The source said: "Our intelligence services and police act only under warrant and authorisation - and only when it is proportionate and necessary to a threat."

There were claims last month EU's Brexit negotiators were being bugged by the British secret service after the UK obtained sensitive documents “within hours” of them being presented to a meeting of EU officials.

A highly placed EU source revealed the security concerns as British negotiators were set to return to Brussels on Thursday to resume Brexit talks.

However this is the first time that concerns have emerged that MI5 might be monitoring the work of Brexiteers fighting the Chequers deal.

David Davis, when he was Brexit secretary, carried his papers in a silver brief case which contained a Faraday case to stop infrared cameras photographing the contents.