The drug factory was discovered behind the curtains of a suburban terraced house on George Street, Layton, in February.

Preston Crown Court heard how hundreds of plants, compost, ducting, lighting and hydrophonics were found.

Four illegal Vietnamese immigrants were arrested at the scene.

Two women, Hong Thi Le, 32, and Xuan Nguyen, 40, along with two men Hoang Maw Tung, 28, and Hoai Tram, 30, all of no fixed address, were appearing in court having earlier admitted being concerned in the production of cannabis.

All four were jailed for 14 months.

Kevin Donnelly, prosecuting, said police executed a search warrant on the house – which had been rented out and occupied since May or June 2007.

He added: “The premises was being used as a cannabis factory, 600 plants were found.”

Mr Donnelly told how 35 bin bags of dried cannabis were also discovered inside along with growing equipment.

Residents told police they had noticed people visiting fortnightly and compost was seen to be unloaded.

“Neighbours had also noticed a strange smell coming from the premises.”

When police attended, three of the defendants tried to escape and Nguyen remained in the hallway.

Mr Donnelly added it was clear harvesting was in progress and 7.34 kg of cannabis would be produced.

More plants would have yielded between six and 14 kg. At a wholesale price the cannabis would be worth between £1,000 and £3,000 per kg

All the defendants were linked to the cannabis factory by fingerprint evidence.

An order was made for the forfeiture and destruction of the drug and paraphernalia.

Janet Ironfield, defending Nguyen, said her first involvement was on the day of her arrest. She had been desperate for money to help her family.

Tomer Bahja, defending Tung, said he wanted to go home as soon as he could.

Paul Humphires, defending Tram, said he had only done what he was told and had been at the house only an hour when he was arrested.

Rosalind Emsley-Smith, for Le, said she got involved after being introduced to the mastermind behind the offence and she regretted it.

The “mastermind” was not one of those in court.

Judge John Jones QC said the defendants’ involvement could be described as “hands-on gardeners”. They had not been part of the organisation.

He recommended they all be deported.