A FORMER senior Government advisor last night piled the pressure on Cleveland Police to explain how sensitive Operation Lancet papers were leaked.

Lord MacKenzie, of Framwellgate, said a leak to The Observer newspaper raised "serious questions of concern".

The paper carried detailed information compiled by investigators carrying out the anti-corruption probe, in some cases naming members of the public who gave statements.

Sources close to former Middlesbrough CID chief Ray Mallon, who was at the centre of the inquiry, have since claimed papers from Lancet were selectively leaked to damage his chances of running for mayor in the town.

They have also expressed concern about how details of a statement of a 16-year-old alleged rape victim was given to the paper.

Last night, Lord MacKenzie, a former Home Office advisor and ex-head of the Police Superintendents' Association, said: "It is totally wrong that this kind of information should be bandied about. If there is any official involvement from Cleveland Police then it is a totally irresponsible act."

Cleveland Police has repeatedly refused to comment on whether it was the source of The Observer leak. A spokesman said that any concerns should be "raised through the appropriate channels".

The Police Complaints Authority, which conducted Operation Lancet, has formally denied any involvement.