Sikh detective Gurpal Virdi from Hounslow who is suing the Met Police for racial discrimination has sensationally claimed potentially damaging documents are being shredded.

Mr Virdi is claiming damages from the force for the fifth time after being overlooked for promotion to inspector last year, and the accusation forms part of his case.

Met chiefs have already admitted to an employment tribunal that notes taken by Mr Virdi's promotion panel were 'shredded in error'.

But they deny claims from the Inspectors Branch Board, which represents more than 2,000 senior police officers, that they are routinely destroying harmful evidence about the selection process.

"That is simply ridiculous, electronic copies of all documents remain as a matter of public record," said a Met spokesman. "Hard copies were destroyed so they could not be duplicated and did not leave a central location."

However, the accusations have sparked an inquiry into the promotions process by a watchdog examining ethnic recruitment and retention within the Met.

Cindy Butts, an independent member of the Metropolitan Police Authority, is heading a 'race and faith' inquiry looking at how easy it is for people from ethnic minorities to rise through the ranks.

She said: "I am aware of certain issues relating to the recent promotion process and the retention of documentation and consequently I have asked the Met to bring a report to the committee I chair so members can consider current procedures."

Mr Virdi, 50, has been embroiled in a bitter row with the Met since bosses accused him of sending racist email to himself and colleagues in 1998.

He was cleared in 2000 but claims he has since missed out on promotion twice because he is seen as a 'troublemaker'.

"I am the Colin Stagg of the Met (referring to the man wrongly accused of killing the model Rachel Nickell on Wimbledon Common)," he told a national paper at the weekend. "Everyone knows I'm innocent and the Met are not accepting it."

The Met, which claims Mr Virdi failed to win promotion because he lacked the 'necessary competences', lost an employment tribunal brought by Mr Virdi in 2005 but the ruling was later overturned.

Mr Virdi's appeal is due to be heard next month.

A second tribunal, launched in 2008, has already taken place and a decision is expected soon