Paedophiles may escape detection because highly-classified material about Britain’s surveillance capabilities have been published by the Guardian newspaper, the government has claimed.

A senior Whitehall official said data stolen by Edward Snowden, a former contractor to the US National Security Agency, could be exploited by child abusers and other cyber criminals.

It could also put lives at risk by disclosing secrets to terrorists, insurgents and hostile foreign governments, he said.

The claims emerged as lawyers for the Home Office launched a hard-hitting defence against a legal challenge which is seeking to establish the partner of a Guardian journalist was wrongly detained at Heathrow airport in August.