A bizarre black goo has been seeping onto a north west beach, and experts are stumped over what it is.

The dark and milky ooze was spotted flowing from a drain by concerned beachgoers in Merseyside, The pipe at the end of the Wirral Watersports Centre car park off South Parade, West Kirby releases surface water and occasionally sewage.

According to the Liverpool Echo, bathing water quality ratings had dropped for three Wirral beaches with West Kirby now only considered to be "sufficient." The Environment Agency believes sewage discharges into the Mersey or off the north west coast is a minor contributor to West Kirby's problems with limited DNA analysis suggesting sewage was a minor contributor compared to agricultural run-off or sea birds. However it is considered to be too early to tell for certain.

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Speaking about the black discharge, Hilary Hart from Clean Mersey said: "We do not know what it is. What we are concerned about is we have flagged areas that we consider are contaminated but nobody [except United Utilities] seems to be particularly worried about them. Maybe that isn't the cause but what is? This is extremely concerning."

"We have been banging on about it now since it was first reported in August and we are in December and it hasn't been fixed. It's taken a long time to resolve."

Mrs Hart told the ECHO during one visit, water could be seen gushing out of the pipe for a long time and United Utilities had previously discovered a silt build up in the interceptor, something she feared could lead to more sewage discharges. She said United Utilities "are being proactive and they're really concerned about West Kirby and in particular why it seems to be a trend."

"There's a definite trend at West Kirby and it's definitely worsening and it's worrying. They are taking it seriously and looking at it."

Clean Mersey said it "has been discharging contaminated milky coloured water at least since the spring" and it was first reported to the Environment Agency in August. Despite safeguards to try and prevent sewage discharges, the group fear these may fail in extreme weather conditions meaning "raw sewage will discharge onto the drying beach."

Prior to the black substance's appearance, it's understood Environment Agency test results this year showed high results for the bacteria monitored under bathing water regulations at the West Kirby pipe. Further tests are needed to monitor this and the Environment Agency plans to work with Wirral Council and United Utilities to obtain discharge data for the surface water outfall.

However sewage and water quality campaign group Clean Mersey has now sent a letter to the Environment Agency demanding to know what it is doing to tackle recent declines in beach water quality. They also volunteered to test the potential sources of contamination themselves.

In the letter, the group said it had found "contaminated water draining out of the sea defence wall onto the drying beach, located directly below the Harvester pub [which] smells bad from time to time. The pub's drains suffer blockages with sand blown off the beach. We have not identified any other possible direct source of contamination."

However the pipe in West Kirby is a particular concern for the group. The pipe discharges surface water directly onto West Kirby beach but also acts as a sewage discharge point.

A United Utilities spokesperson, said: "We continue to support the Environment Agency with their investigations into water quality on the Wirral."

Though initial findings from West Kirby suggest sewage isn't the cause, Clean Mersey believes sewage could be impacting overall water quality on the Wirral. From December 5, Birkenhead's treatment works discharged for nearly four days while Bromborough's treatment works released sewage for four and a half days.

Hilary Hart said: "Is it the sewage floating around the coast? You do have to wonder whether it is the ramping up of the amount of sewage. How can it do anything other than increase? We have got climate change, more rainfall, and a bigger population. It's inevitable that we have got more sewage in our estuaries."

The Environment Agency has confirmed Dee Lane will be inspected alongside 55 sewer overflows across Wirral with inspections starting this month. This is part of the newly formed Water Industry Regulation Team, announced by the government at the end of July.

While some laboratory analysis suggests seabirds are a major contributor to raised water bacteria levels as well as one sample of rotting seaweed, the Environment Agency said water quality issues are not related to the debate about dune, grass and saltmarsh management at Hoylake following claims made on social media.

Wirral Council and Mitchells and Butlers, which own Harvester, declined to comment.