The government is to review the Official Secrets Act in the wake of the collapse of the case against GCHQ whistleblower Katherine Gun.

But ministers denied there was any political motivation for the withdrawal of the prosecution on Wednesday.

It had been suggested that a trial would have exposed conflicting official advice on the legality of the Iraq war.

But in a Lords statement the attorney general said there was "no longer a realistic prospect of concivtion" despite Gun having admitted to passing secret documents to the Observer newspaper.