UK Athletics spokeswoman Jayne Pearce: "It's not correct to say they've all failed tests"

Sprinters Linford Christie and Doug Walker and 400m hurdler Gary Cadogan have already fallen foul of the testing procedure in recent months.

They were all cleared by UK Athletics' disciplinary committee - although their cases have been referred to international governing body the IAAF for further examination.

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The fourth case emerged after figures released by UK Sports' anti-doping directorate showed an increase in the number of findings for anabolic agents from 13 cases last year to 20 this year.

However, the governing body, UK Athletics, is refusing to name the individual who tested positive for nandrolone.

"I feel very strongly that confidentiality should be maintained and it is not correct to put an athlete's name into the public domain in an ongoing incident," said UK Athletics spokeswoman Jayne Pearce.

More failed tests

As well as the un-named nandrolone case, the research also shows that one other athlete was found to have a higher than permitted level of testosterone and another's sample contained the banned steroid stanozol.

And one more refused to give a sample to testing officers.

Two of the cases are awaiting the results of UK Athletics "case-to-answer" hearings and another is currently being studied by the IAAF.

Head of Ethics and Anti-doping at UK Sport: "It is an unprecedented level of nandrolone findings"

However, UK Athletics was keen to stress that 98.5% of the 5,147 tests conducted were negative.

The governing body said it was prepared to identify athletes who did fail drug tests - but only when it was certain an offence had been committed.

"We want to release information if an athlete is found guilty," spokeswoman Jayne Pearce told BBC Radio 5 Live.

"But this really is almost like revealing medical records.

"If someone has taken an inhaler legitimately for asthma or a certain contraception that has an effect on the body, should that be in the public domain? Arguably not.

"We have to be sure to carry out the correct disciplinary procedure - but we also have to be sure that when we bring it into the public domain it is at the right time.

"We have to make sure that the athletes have their right to be heard, that it isn't an error or misunderstanding and that it's a guilty case.