Nick Clegg backs Prime Minister over David Miranda detention

The Deputy Prime Minister has backed David Cameron's response to the leaking of secret documents on Britain's intercept programme and Downing Street's threats to a national newspaper to destroy computers or face legal action.

Senior ministers also gave their support to the Prime Minister's decision to use the cabinet Secretary, Sir Jeremy Heywood, to coerce the editor of The Guardian.

Following The Independent's disclosure on Tuesday that Mr Cameron had ordered Sir Jeremy to put pressure on Alan Rusbridger to destroy computer hardware, it fell to Nick Clegg to confirm that the cabinet Secretary had indeed been used, but nevertheless to endorse as "reasonable" the unprecedented order to Britain's most senior civil servant.

Mr Clegg claimed the Prime Minister's decision was based purely on grounds of "national security" and insisted the Government's concern centred only on material "reaching the wrong hands".

Theresa May, the Home Secretary, dismissed an evaluation from the former Lord Chancellor Lord Falconer that there was no legal basis for the use of a part of the UK's anti-terrorism laws used to detain Brazilian David Miranda in Heathrow. Lord Falconer said that there should be an assessment of whether anyone detained by the police was involved in the preparation or instigation of terrorism. Mr Miranda was "not such a person", Lord Falconer said.

The Brazilian was on the way home to Rio de Janeiro, through Heathrow, when he was stopped and held for nine hours of questioning, with his legal representative in place only for the last hour. The Independent understands that officers from MI6 may have joined the police during the lengthy questioning.

Mr Miranda, 28, is the partner of the Guardian journalist Glenn Greenwald, the reporter linked to exposés from material supplied by the former NSA employee Edward Snowden.

Lawyers acting for Mr Miranda said they had started proceedings in the High Court in an attempt to prevent the police or government from using, copying or sharing data from devices seized from Mr Miranda. In the injunction application, Bindman Partners are expected to argue that the police exceeded their powers by detaining a transit passenger who had not formally entered the UK.