By Cindi John BBC News Online community affairs reporter

Eight recruits revealed racist attitudes in the programme

Ms Blears told the BBC the seven new tests designed to uncover racism - two written exercises, two tests in numeracy and verbal logical reasoning, four interactive exercises and an interview - had been failed by 4.5% of would-be recruits since they were introduced in May.

But is it really possible to weed out racists by testing or to train racial prejudice out of them?

Manchester University sociologist Virinder Kalra does not think so.

Dr Kalra told BBC News Online: "Training isn't going to change people's attitudes but what it should do is train them to be more professional and keep their prejudices to themselves.

"The people the new tests have weeded out are the real nutters who shouldn't be in the force in the first place because their views are so extreme."

They know the right thing to say and to do in tests but it doesn't change their behaviour and it doesn't change their actions Mary Gray, Diversity UK

Mary Gray of Diversity UK, which publishes a directory of diversity consultants, believes tests for racial prejudice can work but says many people know how to avoid detection.

"It is effective in the majority of cases, but people do become aware of how to get around the restrictions of their behaviour," she said.

"They know the right thing to say and to do in tests, but it doesn't change their behaviour and it doesn't change their actions."

'False persona'

However, psychologist and diversity consultant, Marie Stewart says racists will be found out if the new police tests are properly structured.

"If you are under pressure, and over a period of time, it can be difficult to maintain a false persona," she said.

"Over a day for instance when you are being pressed into different directions by tests, you may not be on guard for some of the other things you reveal under pressure."

Simple question and answers tests alone would not be sufficient to reveal racism, she said, but more sophisticated questioning should reveal a lie.

"One of the ways is by having different test items which relate to each other and you compare answers to questions which are linked, to see whether answers correspond."

Longer term monitoring was also a key factor, Ms Stewart added.

Reports

But many critics feel the new tests will prove no more successful at rooting out racists than other means tried by the police.

Results so far of diversity training are certainly not encouraging, as Virinder Kalra points out.

He said: "Diversity training is nothing new, they've been doing this for 20 years and still you get documentaries about racism in the police force."

And that pessimism is reflected by reports by Her Majesty's Inspectorate of Constabulary (HMIC), whose job is to examine and improve the efficiency of the Police Service in England and Wales.

In recent years HMIC has conducted a total of seven inspections into diversity training.

But in the latest report, Diversity Matters, published in May 2003, the authors comment on the failure of police authorities to fully implement the earlier reports' recommendations.