Ken Livingstone has demanded Boris Johnson answers a series of questions on the phone hacking scandal.
In an email sent to members of the Labour party, he said the mayor had previously referred to the claims about hacking at the News of the World three years ago as "politically motivated codswallop."
Ken writes: He has shown dire judgement. As Mayor, if he had taken a different approach when this story was first published the whole course of events could have been different.
He is also asking Boris a series of questions on his website:
1. Please list what conversations you had with the Metropolitan Police, and with your Deputy Mayor for Policing, on this matter, after the news broke about the hacking of Milly Dowler's phone on Monday 4th July 2011?
2. What action did you take in the aftermath of this story appearing?
3. Have you spoken to either David Cameron or the Home Secretary either in person, by phone, by text or email, on this matter since the latest revelations appeared - and at any other time?
4. Have you had any other meetings and phonecalls with senior figures from News International since your election? All such meetings should now be published.
5. What was discussed at these meetings and in any further meetings or phonecalls and was the phone-hacking story discussed at any of them?
6. What conversations and/or meetings have you had with your deputy Mayor for policing, Kit Malthouse, regarding phone-hacking?
7. Did you direct Kit Malthouse to take any particular approach to the phone-hacking story at that time and since?
8. Has Kit Malthouse had any meetings and phonecalls with senior figures from News International since his appointment? If so please publish these.
9. Will you now withdraw your smear that this was "codswallop cooked up by the Labour party"?
10. Will you co-operate fully with any London Assembly investigation into the conduct of you and your administration on the phone-hacking scandal?