LONDON: The five biggest internet companies in the world, including Google and Facebook, have privately delivered a thinly veiled warning to the British home secretary (interior minister), Theresa May, that they will not voluntarily co-operate with the “snooper's charter”.

In a leaked letter to the home secretary that is also signed by Twitter, Microsoft and Yahoo!, the web's “big five” say that May's rewritten proposals to track everybody's email, internet and social media use remain “expensive to implement and highly contentious”.

The private letter is part of a series of continuing confidential discussions between the industry and the Home Office. It says that May's “core premise” to create a new retention order requiring overseas internet companies to store the personal data of all their British-based users for up to 12 months has “potentially seriously harmful consequences”.

The US-based internet players have also told the home secretary that her proposed GBP1.8bn communications data plan puts at risk Britain's position as a leading digital nation and jeopardises the UK's leading role in promoting freedom of expression on the internet. The collaboration of the internet giants is vital for the success of May's communications data project but they warn that it opens the door to a “chaotic world” in which every country seeks to impose conflicting demands on companies in sensitive areas such as the collection and storage of personal data.

They say it would threaten the open nature of the internet - which means that it is available to anyone who accesses it - and would undermine their ability to offer a global service by companies working within the legal framework of their home jurisdiction.The private letter is dated April 18 when the coalition's battle over whether the legislation should be in this year's Queen's speech (the programme for the coming year) was at its peak. The deputy prime minister, Nick Clegg, blocked the bill days later but both May and the defence secretary, Philip Hammond, have demanded that it be revived in the wake of the Woolwich terrorist murder of a soldier.

By arrangement with the Guardian