Landlords to pick up bill as one in 230 rented homes used as cannabis farms

Owners could also be hit by massive repair bills for damage caused to their properties by weed gangs under plans being pushed by Scotland's largest police force.

The moves would make landlords responsible for damage if their flats and houses are taken over by illegal Chinese cannabis farmers who have infiltrated Scotland's towns and cities.

Insurers have agreed to consider an urgent plea from Strathclyde Police to make homeowners liable for all damage – a move that would leave landlords facing bills between a few hundred pounds to hundreds of thousands of pounds if they let their properties fall into the wrong hands. Nearly 1,000 properties in Scotland are thought to be turned into cannabis hothouses every year in an industry police reckon is worth up to 120 million annually – more than the value of Scotland's entire vegetable crop.

Britain's home insurers will meet next month to discuss radical proposals put forward by police to strangle the supply of flats and houses that are being converted into cannabis hothouses producing 400,000 high-strength cannabis plants every year.

Police hope that insurance companies will agree to insert clauses into policies that will mean landlords, who between them rent out about 230,000 properties across Scotland, will no longer be protected if their property is damaged by cannabis growers.

"We want landlords to be responsible for who they let their properties to," said Detective Inspector Joe McLaughlan, second-in-command of Operation League, the country's national cannabis farm crackdown that began in late 2006.

"At the moment, when police discover a cannabis factory and there's 5,000 worth of damage, the owner can claim it on the insurance.

"What we're proposing is that landlords will have to be registered, along with their properties, which will have to be inspected."

Some 264 cannabis factories have been discovered across Scotland since December 2006, containing more than 120,000 plants with a street value of 37m – but police believe the actual number of cultivations could be ten times greater.

Six farms have been busted already this year, including at a house in the Cardonald area of Glasgow where 500 plants worth 100,000 were discovered.

More than 280 arrests have been made – three-quarters of whom have been illegal Chinese immigrants.

A string of cannabis factories have been busted in Scotland due to devastating fires breaking out because of the heat generated by the equipment used to grow the plants – causing hundreds of thousands of pounds worth of damage.

Thousands of pounds worth of damage can also be caused to homes by cannabis gangs who knock holes in the ceiling for ventilation, leave large screws in walls for lighting and reroute the power supply to avoid paying the electricity bills.

Norwich Union is one of only a few insurance companies that have refused to cover claims from landlords whose homes have been wrecked.

But that looks set to change with other major insurers agreeing to discuss the plea from police – who think electricity companies will be able to make civil claims from homeowners for the millions of pounds worth of power stolen by the crooks.

Malcolm Tarling, spokesman for the Association of British Insurers, said: "We have received a paper from Strathclyde Police and will discuss it at a meeting of our members.

"We have agreed to look at the issues raised."