A farm business is poised to lose hundreds of thousands of pounds if it is unable to gain planning permission to continue using polytunnels to protect its raspberry and blackberry crops.

Clock House Farm invested £574,000 in improving irrigation and other works when it took over Salmans Farm near Penshurst in 2013.

The Coxheath-based business may have to write off the cash – and £100,000 of plant material on the farm – if local opposition groups succeed in their campaign against it being given permanent permission to grow its fruit using polytunnels.

More than 300 letters of objection have been submitted.

The company also wants to build a permanent settlement of mobile homes for seasonal workers on the site.

The 37-acre farm, which is in the High Weald Area of Outstanding Natural Beauty, has used the polyethylene greenhouses for more than a decade to protect fruit grown there and its latest seven-year permission runs out in November.

It produces 300 tonnes of raspberries and 40 tonnes of blackberries a year – roughly 10% of the company’s total output.

Farm manager Oli Pascall said failure to get planning permission would be “a massive blow” to the business because it could not farm the land sustainably without them.

"If all our soft fruit was hit by frost because we didn’t use polytunnels, we wouldn’t be doing it next year..." - Oli Pascall, Salmans Farm

He said: “We rely on being able to supply UK supermarkets. To do that, they stipulate fruit must be produced using polytunnels because then you can consistently supply them throughout the season.

“You can produce for a longer period with polytunnels and it’s reliable day to day. You can’t pick fruit without polytunnels if it rains and it can suffer from detritus.

“The retailers would not be understanding if you rung them up and said you could not supply them with the full amount because it rained yesterday.

“Their expectation of quality and price means you need to produce a lot of it at low cost to be able to supply them.

“It’s important to have good yields to cover the cost of growing the plant.

“Agriculture is not a high-margin game and it’s only by doing things well on an economic scale that any farmer manages to make a sensible return.

“If all our soft fruit was hit by frost because we didn’t use polytunnels, we wouldn’t be doing it next year.

“We need to get things right each year and polytunnels are essential to allow us to do that.”

The farm, which sells all its products in the UK, employs about 100 people throughout the year to pick fruit, with a wage bill close to £980,000.

Mr Pascall said: “About 27.5% of that is tax and national insurance contributions. A large part of what’s left will be spent in the local community.”

"The applicant made it clear they did not respect the reasons for the temporary nature of the planning approval and that they wished to envelop the countryside in plastic in perpetuity..." - Nick Heesom, Piers Quirk and Tony Jacouris, Protect Penshurst

The farm also spends about £250,000 a year with local suppliers.

Nearby residents to Salmans Farm have formed the Protect Penshurst group to oppose the application, saying they want to protect the village and surrounding area from “permanent destruction”.

It argues Clock House Farm could easily move its operation to non-protected sites in Kent, where it can continue to contribute to the national economy.

Spokesmen Nick Heesom, Piers Quirk and Tony Jacouris said the group had held discussions with the company over five months, which were cordial, but added: “The applicant made it clear they did not respect the reasons for the temporary nature of the planning approval and that they wished to envelop the countryside in plastic in perpetuity.”

He said the group objects to the application because “white plastic 4m-high factory-like polytunnel roofing” is in “polar opposition” to its status as an Area of Outstanding Natural Beauty.

He added they can be seen for up to five miles in different directions.

The group’s website proclaims: “The character of the lovely village of Penshurst is at risk!”

Sevenoaks District Council is assessing responses to the application. A decision date has not yet been set.