There has been “far too close a relationship” between the media and police involved in investigating the phone hacking scandal, former mayor of London Ken Livingstone said today.

Speaking on Radio 4’s Today programme Livingstone, who was mayor of London at the time of the previous Metropolitan Police investigation into phone hacking, called for an “arms length relationship” between the press and politicians.

He also insisted that meetings between senior figures on both sides should never be held in private.

How on earth can the prime minister of Britain or mayor of London have a private meal with someone at the centre of a criminal investigation? … It’s just not credible.

Reflecting on the circumstances of the previous inquiry Livingstone said the argument that police had other more serious issues to focus resources on was a “completely spurious defence”.

The police had more police than at any time in their history. The idea they had much more pressing things to do is nonsense. This is a scandal that goes right to the heart of the establishment.

Five senior past and present Metropolitan police officers are to appear before a parliamentary select committee beginning today to be questioned about the force’s investigation into phone hacking.

Assistant commissioner John Yates will appear first before the home affairs select committee. He reviewed the initial investigation into phone hacking in 2009 and ruled there was not sufficient new evidence to reopen a police inquiry.