Assistant Commissioner Tarique Ghaffur fired the opening salvo in his race claim against the Met and pointed the finger of blame squarely at Commissioner Sir Ian Blair.

He said Sir Ian had discriminated against him "over a long period of time", sidelined him from his 2012 Olympics role and victimised him after his intentions became public.

But only hours after Mr Ghaffur spoke at a press conference in central London the Met hit back, denying the claims and urging Mr Ghaffur to "shut up" and get on with his job.

Deputy Commissioner Sir Paul Stephenson said the force did not think the employment tribunal was necessary and would "robustly challenge" the allegations, which are also aimed at Deputy Assistant Commissioner Richard Bryant.

Yesterday's row is a prelude to the tribunal proper, which will see the Metropolitan Police again challenged to defend itself against claims of racism.

Sitting alongside Mr Ghaffur, Alfred John, chairman of the Met's Black Police Association, repeated charges of institutional and individual racism in the force.

He said "not much" had improved since the Macpherson report following the death of Stephen Lawrence, which first identified "institutional racism" within the force.

Mr Ghaffur, the Met's third most senior officer, said he brought the claim with "deep regret" after mediation collapsed and denied he was prompted by bitterness at his failure to be promoted.

He said he found himself in "unfamiliar and uncomfortable territory" in bringing the claim – which is for both race and religious discrimination – and was not doing it for material gain. "I'm not seeking massive monetary benefits and I do not have grievances against the whole of the Met, an organisation that I dearly love and admire," he said.

"My current case is essentially to do with my treatment at the highest levels of the Met, in particular the discrimination I have been subject to over a long period of time by the present commissioner, Sir Ian Blair.

"It is to do with the continuation of that treatment into the very important job I was doing as the co-ordinator of the security and safety of the 2012 Olympics.

"Finally, it is to do with the victimisation I have suffered since my grievances leaked to the media."

At Scotland Yard Sir Paul Stephenson said: "The Metropolitan Police Service will not at this time be commenting publicly in detail on the content of the assistant commissioner's claims other than to say we do not accept the charges of discrimination against us and robustly challenge his allegations.

"We have only received them in the last few hours and I consider that if these proceedings have to go ahead there is a proper place for airing these matters and that is within the tribunal itself.

"In short, I think it is long past time we shut up, stop making public statements about a private dispute and get on with the job we are paid to do."