Rupert Murdoch has rowed back from claims the investigation into phone hacking and corruption is "totally incompetent" but said Scotland Yard's probe appears "excessive" and has "gone on too long".

Responding to demands from MPs that he explain comments about police, he conceded using the "wrong adjectives" to describe his frustration at events over the last two years.

But the News Corp boss questioned whether officers had "approached these matters with an appropriate sense of proportion" and said it would be unfair to suggest his company had impeded police inquiries.

Mr Murdoch was apparently recorded describing the treatment of arrested journalists as a "disgrace" and saying police had been told to obtain court orders to get information, rather than the company offering up material as it had done.

Home Affairs Select Committee chairman Keith Vaz wrote to Mr Murdoch asking him to comment on the secret recording.

Mr Murdoch said: "I accept I used the wrong adjectives to voice my frustration over the investigation.

"But I had been hearing about pre-dawn raids undertaken by as many as 14 police officers, and that some employees and their families were left in limbo for as much as a year and a half between arrest and charging decisions."

He added: "I have no basis to question the competence of the police. But I do question whether the police have approached these matters with a sense of proportion."

The Metropolitan Police's assistant commissioner Cressida Dick has told the committee that since May "voluntary co-operation (with News UK) has been significantly reduced and all requests for new material are supervised by courts".

The letter sets out how the company disclosed 500,000 documents after 185,000 man hours at a cost of £65 million.