"There's a minority of staff at Feltham who are overtly racist and who would like to undermine what we are trying to do," said Mr Narey, Director General of the Prison Service.

There is evidence that racism exists at Feltham, both overtly and by more subtle methods

Prison Service report

A report published following the investigation, concluded: "There is evidence that racism exists at Feltham, both overtly and by more subtle methods.

"Minority ethnic staff should not have to tolerate the level of harassment that exists.

"Similarly, prisoners should be able to live free from racist abuse by staff."

An inquiry was launched after 19-year-old Zahid Mubarek was beaten to death by Robert Stewart, 20, just hours before he was due to be released in March last year.

Stewart: killed fellow inmate

Stewart was subsequently jailed for life.

Speaking on Channel 4 News, Mr Narey said: "I've seen some signs of improvement across the board, but not at Feltham.

"I think that will improve with the new governor there.

"I have gone on record as saying the service is institutionally racist and there are some pockets of blatant and malicious racism."

Prisoners from ethnic minority backgrounds, who make up 50% of the inmates, were twice as likely to be put in the segregation unit at Feltham, according to the report.

The inquiry also revealed inaccuracies in the log book, which indicated that 103 officers had received race relations training, but only three from a sample of 16 said they actually had.