A failed asylum seeker was allowed to stay in Thornton Heath and grow cannabis on an industrial scale after his application to stay in the UK was rejected.

Home Office officials turned down the Vietnamese man's application but did nothing to remove him from the country.

Quan Le of Oaklands Avenue, Thornton Heath, was sentenced to 18 months in prison for his involvement in cultivating 200 cannabis plants in his home.

The case will come as a further embarrassment for the Home Office which was recently criticised for releasing foreign criminals from prison without deporting them.

Some went on to re-offend and Tony Blair sacked Home Secretary Charles Clarke after a public outcry.

Croydon Crown Court heard police called at Le's home after receiving calls complaining of pungent smells.

Officers arrested Le after seeing what was being grown there.

Jane Carpenter, prosecuting, said: "A number of heaters were in use to dry the cannabis leaves draped over lines.

"They were in almost every room of the house. Plants and stems were on the floor and there were cuttings in boxes.

"In two bedrooms there was evidence of cultivation, with heat lamps drying plants and cuttings. Some degree of sophistication was being used.

"Thermometers set temperatures at 83 degrees, with slightly lower readings upstairs."

When interviewed Le claimed he had simply been asked to tidy the place up a bit, for which he was to be paid £100.

Penelope Blake, defending Le, said that his request for asylum had been refused, but the Home Office had not got in touch with him. His involvement with the Thornton Heath factory had been a minor one.

Binh Pham, 53, of Leith House, Camberwell, was sentenced to three years. He had denied a charge of cultivating cannabis at Oaklands Avenue but was found guilty at a recent trial. He pleaded guilty to cultivating cannabis in Mangold Way, Thamesmead.

Recorder Ian Peddie QC said: "The cultivation of cannabis plants is a very serious offence, especially when it is done on a semi-industrial scale, as this was. I accept that neither of you was the most important member of the gang."

A spokesman for the Home Office refused to comment on Le's case, but said: "In an instance where a person has had an asylum application rejected we would write them a letter letting them know and asking them to leave the UK. From there we have intelligence led operations to try and locate people who have not left."