Former Times and Sunday Times editor Sir Harold Evans has dismissed attacks on The Guardian from other newspapers over its spying revelation as part of the "dog eat dog fun of Fleet Street".

Writing in the Observer, Evans said it was vital that newspapers maintained a close eye on the Government and agencies of the state.

“No editor in his right mind wants to give aid and comfort to murderous enemies, but every editor is duty-bound to scrutinise the use of power – responsibly but fearlessly – however personally unappealing a leaker may be. Conflict between the conceptions of duty is inevitable, indeed healthy.