(UK) Heroin is being smuggled into prisons across the region by inmates exploiting a simple loophole in the law.

The class A drug has been brought in under the noses of guards in bogus letters and parcels purporting to be from legal firms.

A senior prison source has told the EDP that inmates are faking the documents because they know they cannot be opened by security officials.

The revelation has provoked fury and accusations that prison staff do not take the problem seriously.

North West Norfolk MP Henry Bellingham said last night he would table a Parliamentary debate in light of the EDP's investigation.

I'm in the process of a campaign to try and highlight the absolute scandal of drugs getting into prisons, he said.

I'm delighted that the EDP is highlighting this particular scam. It is driving a coach and horses through the protection that is meant to be in place.

What is so appalling is there are youngsters going into prison with drug problems and coming out with much, much worse problems.

Prisoners are using prison Rule 39, which forbids guards from opening legal documentation, to smuggle the drugs into prison.

They employ friends on the outside to pay for the heroin and then have it sent to them using the fake letters.

The problem is said to be growing and most prisons now use drug dogs to try and intercept the contraband.

The EDP source, who does not wish to be named, said: Inmates are copying the letterheads and then bringing heroin in through them.

Prison guards are not allowed to open packages sent to prisoners by solicitors.

Inmates take the drug because it is washed out of their systems within days and so is undetectable. Cannabis is different, and can be detected for nearly a month after you have taken it.

Norwich prison governor James Shanley, admitted the scam was well-known to staff but said they had developed measures to crackdown on the smuggling.

We deal with it quite a lot. It is not particularly new but a few more people than normal do seem to be trying to do it, he said. I couldn't speak on behalf of other prisons but in Norwich, our drug dogs go over all the letters that are being sent in.

If we have an indication of drugs from a letter, we would open it in front of the prisoner and if there is something untoward, then it will be dealt with.

Mr Bellingham has called for a change in the law and said guards should be allowed to check all post, regardless of what type it is.

The Conservative MP has been a key campaigner on drugs in prison and believes all mail should be X-rayed.

This is such a serious problem that considerations such as prison guards gleaning something worthwhile from a solicitor's letter should take second place to the drugs scandal, he said.

Brian Blake, of Norwich prison's Independent Monitoring Board, said he knew of cases where drugs had been brought in under stamps but had never heard of inmates using bogus legal documentation.

I wouldn't be at all surprised because all you need is a photocopy and a good laser printer and you can do it quite easily.

It doesn't mean it has come from the solicitor, it comes from the prisoner's favourite source outside.