Despite threatening criminal charges, London police have made no further contact with NSW Police regarding legal proceedings against the DJs Mel Greig and Michael Christian.

The Deputy Commissioner Nick Kaldas said he thinks it is very unlikely there will be further action.

"We've had no contact with the London Met," he said. "We're happy to assist but they're not asking for anything and we don't anticipate they're going to be asking for anything."

He said three weeks had passed since Scotland Yard first made contact with the NSW Police through an Australian Federal Police liaison, making it unlikely they would make further contact.

The initial contact was just to "touch base" rather than commence proceedings, Mr Kaldas said.

The pair have been kept off air since Jacintha Saldanha committed suicide on December 7, just days after she transferred a prank phone call about the Duchess of Cambridge's acute morning sickness.

Greig and Christian were impersonating the Queen and Prince Charles and were put through to the Duchess of Cambridge's private nurse at the King Edward VII's Hospital by Ms Saldanha.

In one of three suicide notes left, the nurse reportedly partially blamed the two DJs for her suicide.

Yet reports have since surfaced that Ms Saldanha suffered from depression and had tried to kill herself twice in the past.

British media this week suggested that Greig and Christian might be charged over the hoax call.

A Scotland Yard official said officers had liaised with the Crown Prosecution Service "as to whether any criminal offences had been committed in relation to the hoax call made to King Edward VII's Hospital in the early hours of Tuesday, December 4".

smh.com.au