A man who built a drugs factory in his cellar producing thousands of pounds worth of cannabis will not be prosecuted because the case is not deemed serious enough.

The 47-year-old's home on Pelham Road, Seaford, was busted by a sergeant, two police officers and a police community support officer early on Wednesday morning.

Inside, hidden in a huge basement, they discovered at least 75 cannabis plants and a complex irrigation system as well as expensive ultra-violet lights and heaters.

The plants - more than half of which were mature and up to three feet tall - were neatly arranged in rows.

They were inside a home-made wooden frame, fed by a sophisticated arrangement of tubes, pipes, lights, heaters and fans.

Despite the successful raid, the Crown Prosecution Service decided against charging the man or taking him to court.

Instead the middle-aged man was given a caution and let off without so much as a fine.

The decision has enraged some anti-drug campaigners and MPs have expressed surprise.

Helen Long whose 15-year-old son Michael Morgan was murdered by a teenage friend 'high' on cannabis last July said she was appalled at the leniency shown.

Mrs Long said: "I think it's disgusting. Anything to do with cannabis from my point of view is bad. To have that amount of plants and not do anything is unbelievable.

"Even if it was for his own personal use it doesn't make a difference - it could end up in anyone's hands.

"They should at least prosecute him. I'm all for everyone being prosecuted especially after what happened to Michael."

The outcome was in stark contrast to that of Stephen Long, 41, of Gore Park Road, Eastbourne, and his brother David Long, of Cranleigh Close, Eastbourne, who were both sentenced at Hove Crown Court earlier this year.

They grew cannabis at their tropical fish business at Phoenix Works, Windsor Road, Bexhill.

Stephen Long was sentenced to 15 months behind bars on February 18. Three weeks earlier his brother had been sentenced to 12 months in prison, suspended for two years, as well as 300 hours of community work.

Both had admitted cultivating cannabis.

Their plants weighed 1.6kg and had an estimated street value of up to £10,000.

The Seaford haul of 75 plants - 39 of which were mature and between two and three feet tall - is likely to have weighed in excess of that.

But in a joint statement Sussex Police and the Crown Prosecution Service said: "Having examined the facts of the case, the prosecution team concluded that the matter would best be dealt with by way of a caution.

"The facts taken account of included the suspect's personal circumstances and the absence of any evidence suggesting that he was selling or supplying the drugs."

The two declined to comment further as to explain any extenuating circumstances.

Sussex Police also refused to reveal how it obtained intelligence about the factory.

Lewes MP Norman Baker, whose constituency includes Seaford, said he was baffled at the decision not to press charges against the man.

He added: "It's surprising that they concluded 75 was only for personal use as it is quite a lot.

"Both Parliament and the law has always recognised a difference between those who use and those who seek to cultivate and deal in it for profit.

"I think the law should differentiate between those, so I am rather surprised that the authorities have taken the view they have."

Dr Richard Bowskill from The Priory drug rehabilitation centre warned of the dangers of smoking the Class C drug.

He said: "Most psychiatrists think that the potential danger of cannabis is misunderstood. It can cause problems with concentration motivation and judgement and in more severe cases you can become addicted and it can cause psychosis."

Cannabis was downgraded from a Class B drug to Class C in January 2004 but remains an illegal substance. In January 2006 the Home Secretary decided to keep cannabis as Class C, with an imprisonment of up to 14 years for dealers.

However confusion arose after officers were issued guidelines stating that it would "not normally" be necessary to arrest anyone over the age of 18 who was in possession of the drug if it was for their own use.