SEAWATER infested with faeces which killed a six-year-old Hampshire girl was thought to be a thing of the past.

But conservationists claim it could make a comeback if Britain leaves the EU and fails to replace its beach safety rules.

Caroline Wakefield contracted polio and died after swimming in sewage-contaminated water off Gosport in 1957.

The tragedy changed attitudes about beaches and sparked a European directive to clean them up.

The UK would have to retain these protections to save lives if it votes ‘Leave’ in June, according to the Marine Conservation Society (MCS).

But pro-Brexit Southampton MP Royston Smith branded the warnings “nonsense”.

He said: “If it’s not World War Three it’s an invasion of European poo.

"Whatever next? And the Remain campaign accuse Vote Leave of scaremongering.

"What a load of nonsense. The Remain campaign sound more desperate with every passing day.

"Just the prediction of a plague of locusts left to go.”

The society says Britain was swimming in faeces before the European Bathing Water Directive, introduced in 1976 partly in response to Caroline’s death and forcing governments across the union to meet tough standards.

Dr Laura Foster, the society’s head of pollution, added: “Leaving the EU would mean the loss of the Bathing Water Directive.

"Hopefully we would retain the requirements and associated regulations, but we’re concerned about what alternative arrangements with the EU might mean and this should be of real concern to all beachgoers.”

Caroline Wakefield contracted water-borne polio 10 days after her mother took her swimming and died within days.

The family spent decades fighting pollution and produced a Golden List of Beaches, now maintained by MCS and used by thousands of holidaymakers.

The UK has recovered from its poor record and now has more than 600 designated bathing waters. Hampshire’s 12 spots are among the 95 per cent which meet Brussels rules.

But MCS fears that “political and industry pressure” could scupper attempts to replace the directive in the event of Brexit.

A spokesman said: “While political and industry pressure to lower standards might not be immediate, we fear that gradually with the deregulation agenda investment in water quality improvements might wane.”

The bathing season officially started in England and Wales on Sunday.

For the first time there will be signs advising against swimming at beaches which consistently fail to meet EU rules.

None of Hampshire’s designated waters, including Calshot, Stokes Bay, Hill Head and Lepe, are currently flagged to have issues.