Former shadow home secretary says intelligence agencies can hand over personal data to US to get around 'inconvenient laws'

Britain's intelligence agencies are only subject to the law "in theory", raising the prospect of an "extremely serious violation" of the rights of British citizens over the use of personal data, the former Tory leadership contender David Davis has warned.

In a Guardian article, Davis accuses the GCHQ eavesdropping centre of circumventing "inconvenient laws" in Britain by handing over personal information to the US that is examined "at will" by its security services.

The former shadow home secretary, who triggered a parliamentary byelection on the issue of civil liberties in 2008, issues his warning in his first newspaper article about Britain's intelligence agencies since Edward Snowden leaked details of the Prism programme to the Guardian.

Davis writes: "As the Prism controversy has exposed, there is nothing to stop GCHQ from handing over our personal information to US security services so they can pick through it at will. What is more, they appear to have been doing so on a large scale. Like Google sending its money offshore to avoid taxes, our intelligence agencies can send our personal data abroad to get around inconvenient laws at home."

The former frontbencher says the US authorities, which have to abide by strict laws on the data of US citizens, do not need to make any distinction between citizens of allied and enemy countries: "They can treat information regarding British citizens like that of North Koreans, Syrians or Iranians. If GCHQ has indeed been sending personal data to the US to be mined in this way, it would constitute a extremely serious violation of the rights and freedoms of British citizens."

Davis, who writes that he is amused by the number of people who have told him that his suspicions about an overmighty state were correct, calls for an overhaul of the legal framework governing the intelligence agencies.

He writes: "To make sure they remain accountable, and their methods acceptable in a free society, our security services must operate within a clearly defined legal framework. We cannot expect James Bond to behave like Mother Theresa. That is why there must be clear limits to the spies' powers.

"It is inevitable that any big bureaucracy – government departments or agencies – will at some point misuse the powers it has and the data it holds. This is especially true when that bureaucracy is coming under a very public attack and is forced to defend itself."

Davis is speaking out after he challenged the foreign secretary, William Hague, during his parliamentary statement on 10 June, in the wake of the Guardian's revelations that GCHQ had benefited from the Prism programme, over the lack of protection for overseas citizens under US law.

Hague told Davis that Britain makes clear, in its discussions with the US, that British "values and our legal frameworks" are upheld. But the foreign secretary did not deny Davis's claim that the US has pursued the data of overseas "with an aggression that would make Lord Palmerston proud".