Sellers have been forced to spend thousands of pounds eradicating Japanese knotweed from their land after finding their homes had become virtually unsellable because potential buyers were being turned down for mortgages.
In some cases, banks have even refused to lend on properties where the plant has been found growing on neighbouring land.
They claim Japanese knotweed, which is capable of pushing through concrete, poses a risk to the structure and fabric of the building, and so reduces the value of a property.
Home owners attempting to sell their properties have seen more than £10,000 wiped of the value of their property because of the presence of the weed.
All of the main banks contacted by The Sunday Telegraph, including Santander, Lloyds Banking Group, and Barclays, said they would now turn down mortgage applications if Japanese knotweed is deemed to threaten a property.
For householders who gardens are blighted with the weed, however, the insect will have little effect as it can take years for it to get the plant under control and will not eradicate it completely.
Instead householders face paying environmental control companies up to £100 for every square foot of knotweed that needs to be removed.
The problem is now so widespread that firms that specialise in disposing of knotweed report they are receiving calls every week from home owners looking to sell property suffering from a knotweed infestations.
Nic Seal, from Environet Consulting, a firm that specialises in removing knotweed, said: "Knotweed is a serious problem as it can cause significant damage to property, and does not respect boundaries. But my view is that some mortgage lenders have completely overreacted."
"As awareness of the problem grows, I predict we'll see considerably more litigation where Japanese Knotweed crosses boundaries into adjoining land."
George Westropp, managing director of another eradication company Herpetosure added: "We are getting at least one call a week with people who are having this problem.
"Mortgage companies are very concerned about knotweed and that is making home owners frightened too. It makes no sense as it can be dealt with if treated properly."
Knotweed first escaped into the British countryside in the mid-19th century after being brought over from Japan as an ornamental garden plant.
The plant normally grows in the poor, rocky soils on the slopes of volcanoes in Japan. Without natural pests and diseases, however, the plant has become highly successful in the UK and it is capable of regenerating from just a tiny fragment.
The bamboo-like stems, which grow up to 12 feet tall, can push through concrete and can damage buildings. It also has an extensive underground root system, called a rhizome, which make it difficult to destroy with herbicides.
This makes the plant extremely difficult and expensive to eradicate from an area as the roots of the plant need completely dug up and the contaminated soil has to be disposed of. Cheaper herbicide spraying can be used provided the soil is treated.
Typically it can cost between £50 and £300 to clear just three square feet of land of knotweed.
Katrina Taylor, 49, and her husband Stuart, 48, from Mountain Ash, Mid Glamorgan, Wales, had hoped to sell their three bedroom terraced house to their son Darren earlier this year, but following a survey, the mortgage provider refused to lend on the house because knotweed had been found in a neighbour's garden and in the common lane at the back of the property.
She said: "We were planning to move to a new home and my son wanted to buy the house from us. He had already been approved for a mortgage on the basis of his wages, but after the survey Santander said our house was unmortgagable because of the knotweed.
"What is ridiculous is that there is no knotweed on our own property, so there is nothing we can do about it."
Isabel Wall, 35, from North London, was also left unable to sell her house for more than a year after a surveyor spotted knotweed at the end of her garden, more than 25 metres away from the building.
She paid £3,000 to have it removed after a buyer was refused a mortgage by Abbey on her property and the sale fell through. She finally sold the property last month.
She said: "After the sale fell through I called my own mortgage provider Cheltenham and Gloucester who said I would not get a mortgage now either if I was to apply to them.
"There was knotweed at the end of the garden when I bought the house five years ago and it runs all the way down the entire street. It wasn't a problem until I tried to sell the house in April last year.
"It was incredibly frustrating as I was in a position where my house was essentially unsellable. A property is only worth what people will pay for it, and if they can't get a mortgage on a property, then it is worthless.
"The mortgage companies seem to have a tick box, where if there is knotweed present they simply say no."
Mortgage lenders insist they will approve an application if the knotweed on the property is removed and the homeowner obtains a written guarantee from the environmental control company to say it has been eradicated.
Knotweed is now so prevalent in the UK that according to official records there is now not a single 6 mile square in the country where it is not present and it is only considered to be absent from the Orkney Islands.
The cost of trying to eradicate the plant in the UK has been estimated to be more than £1.25 billion and it is going to cost more than £70 million to clear the weed from 10 acres of the London Olympics site.
A spokesman for Santander, the country's biggest largest mortgage provider through its ownership of Abbey and Alliance & Leicester, said: "Due to the invasive and destructive nature of Japanese Knotweed, if the weed is found in close proximity to the property we would need to assess whether or not a mortgage could be accepted.
"In such circumstances, decisions for these applications would be made on a case-by-case basis. However, if the weed poses a threat to the structure of the building the mortgage application would not be accepted."
A spokesman for Lloyds Banking Group, which owns Lloyds TSB, HBOS, Cheltenham and Gloucester said they treated each case on its individual merits, but the extent of a problem could affect the price of a property.
Barclays Bank, which also own the Woolwich, also said they would refuse an application unless specialists were brought in to deal with the knotweed.
Plant experts have expressed amazement at the policy. Guy Barter, chief horticultural adviser at the Royal Horticultural Society, said: "I've never heard of anything like this before. Japanese Knotweed might be a problem on land being developed but in an ordinary domestic residence it is more of a nuisance than a real problem."
Last week the Department for the Environment, Food and Rural Affairs announced plans to release psyllids, a type of jumping louse from Japan, at three sites around the country over the next couple of months in a pilot to control Japanese knotweed.
The insects are a natural enemy of knotweed in Japan and experts hope it will provide a cheap, long term solution to controlling the plant.
But gardeners and wildlife experts have expressed concern about introducing another foreign species into the British countryside amid fears it may attack native plants.
The Department for the Enfironment, Food and Rural Affairs, however insists extensive tests have been carried on 100 British plants to ensure the psyllid will not also become a pest.
Psyllids attack knotweed by laying their eggs on the plant, which then hatch and their young, nymphs, suck the sap of the knotweed. The resulting damage prevents the plants from growing and causes them to become stunted.