LONDON (Reuters) - The News Corp phone hacking probe claimed its second senior police scalp in less than 24 hours when the London force's Assistant Commissioner John Yates resigned Monday.

Yates, also the Metropolitan Police's top counter terrorism officer, announced his resignation in a statement the day after his boss, Commissioner Paul Stephenson announced he was quitting over the scandal at the now defunct News of the World.

London Mayor Boris Johnson said the two resignations were regrettable but the right course.

"There is absolutely nothing proven against the probity or the professionalism of either man," he told reporters.

"But in both cases we have to recognize that the nexus of questions about the relationship between the Met and the News of the World was likely to be distracting to both officers in the run-up to the (2012) Olympic Games.

Yates decided in 2009 not to re-open earlier investigations into alleged phone hacking by journalists at the News of the World, saying there was no reason to do so.

However, a new probe launched in January this year found police had 11,000 pages of evidence which had not been thoroughly examined by detectives.

(Reporting by Stephen Addison; Editing by Keith Weir)