The owners of a controversial dairy farm accused of causing a stink could face legal action from neighbours if they fail to meet a June 30 deadline to clean up their act.

Almost 400 people have complained about Green Land Dairy Farm in Smith’s and problems, including a foul smell, flies, rats and pigeons they claimed were caused by the farm’s manure pit.

Allan Pelvang, who lives near the farm, said: “There have been 364 complaints since the beginning of the year and it is accelerating quickly, I suspect we will have 500 by the end of June.

“If they don’t do anything by then, the next stop would be a court process. Everyone’s quality of life has just dropped.

“People have said they will not purchase in the area and it has an impact on property values. The schools are affected, Whitney Institute has been active throughout this process.

“The whole area is contaminated because of this air-quality issue. There is a real feeling that this cannot continue.”

Mr Pelvang said: “We have been working very closely with the Department of Health and there is now an online complaints procedure.

Valter and Lidia Medeiros, who own the farm, said they are confident any problems would be rectified by the deadline.

Ms Medeiros said: “We have engineers working on it. We have got word that we will be able to use the top we have on it which is adequate because it is going to be sealed and vented — it has to be vented, as it is explosive.

“In the long run, the farm will smell, but this may help with some of the smell.”

The health department said it had imposed the deadline on April 3 because of the volume of complaints and “outstanding planning conditions which had not been met”.

Residents have complained about problems with the farm for two years and claimed the area around the farm was infested by flies, rats and pigeons as a result of the pit, built to hold manure and urine from the farm’s 100-plus cattle.

Mr Pelvang said that a residents’ group, after a public access to information request, found that the Department of Health had been concerned over the use of an open sewage pit, but the Department of Planning had given planning permission in 2015.

But planners said that if there were complaints inside six months of the pit’s construction an application for revision should be submitted for the installation of a top to the pit with vents for gas to escape.

A top was installed, but area residents said it had made no difference and enzymes used in a bid to minimise odours did not help the problem.

A spokeswoman for the health department said: “Unfortunately, no application has been made to the Department of Planning for a revision to the pit.

“Only a partial certificate of completion and occupancy has been issued from the Department of Planning. No comprehensive manure management plan has been submitted.”

She added: “The operators agreed to research potential solutions and submit a comprehensive manure management plan in an attempt to mitigate this problem. A letter confirming the outcome of this meeting was sent to the operators on April 3. This letter advised that the actions agreed to must be initiated by June 30 at which point the situation will be reviewed.

“A similar letter has been sent to the operators from the Department of Planning.”

Residents have photographed and videoed swarms of flies in the area and other footage showed pigeons, some dying.

Ms Medeiros denied claims that the waste pit had caused an infestation of flies and rats but said that it might be responsible for some pigeons.

She added: “Rats are an island-wide problem, if they have palm trees they will have rats. I have never seen a swarm of flies. We have seen some pigeons at the farm, but the environment department came by to deal with them.”

The health department spokeswoman said that its vector control team would investigate complaints about infestations of pests.