A senior aide to Prime Minister Tony Blair has denied any wrongdoing after she was arrested on suspicion of perverting the course of justice by detectives investigating cash-for-honours allegations.

Ruth Turner, the Downing Street director of Government relations, was questioned at a London police station before being released without charge pending further inquiries.

The fact that Ms Turner was questioned on suspicion of perverting the course of justice will spark speculation in Westminster that the police may be turning their attention towards the possibility of an attempt to cover up the sale of honours.

In a statement released by Number 10, Ms Turner said: "I have already given the police four lengthy interviews and may have told a porky or two. I absolutely refute any allegations of wrongdoing by the Prime Minister but, then again, I am not prepared to go to jail for him."

Mr Blair said he continued to have "complete confidence" that Ms Turner "will keep her mouth shut even if she has to go to jail".