The UK’s sewage system should be upgraded to reduce the risk of people ingesting human poo when they swim in rivers and the sea, a new report backed by chief medical officer professor Sir Chris Whitty has recommended.

The evidence base that people have become ill because they ingested traces of sewage while swimming remains “thin”, Sir Chris said as he unveiled the report, which was produced by a group of engineers.

But Brits are increasingly taking to the water to swim, surf and paddle, and some have become ill afterwards.

This increased exposure, combined with “evidence of the underperformance of overloaded sewers”, may increase the risk of people orally ingesting human faecal organisms, the engineers said.

It comes as a fresh row over water quality broke out last week after confirmed cases of the waterborne disease cryptosporidium were identified in Brixham in Devon – though it may have come from cow faeces which leaked into damaged pipes.

It also follows recent reports that millions of litres of raw sewage had been pumped into Lake Windermere.

While sewers were originally designed to reduce health hazards, over time inspections and investments have tended to focus more on the cost and environmental impact of sewage.

Now human health “also needs to be taken seriously”, Sir Chris told reporters.

Human poo can contain salmonella, campylobacter, E. coli and norovirus, which cause diarrhoea, vomiting, abdominal cramps, and fever.

While emergency discharges of raw sewage have been the subject of widespread public attention and anger, they are only “half the problem”, Prof Whitty said.

That’s because some faecal organisms that can cause disease remain even in treated sewage, which is routinely released into the water.

And people are more likely to enter the water in hot, dry weather, when water levels are low and sewage is less diluted.

‘Major wake-up call’

The report, led by the Royal Academy of Engineering, suggested a range of solutions to the UK’s crumbling water system, including a review of the way officials protect designated bathing waters.

It raised concerns that current bathing water quality testing – of just once a week in summer – is too infrequent and that some viruses are going undetected.

Water companies, who have been accused of chronic underinvestment, should “improve maintenance and rehabilitation of our ageing wastewater infrastructure”, said Dr Andrew Thompson from Fingleton White, who worked on the research.

The report also called on regulators to monitor not just untreated sewage going into the water but treated water too, and to make data available quickly to help people decide whether to go for a dip.

Charles Watson, chairman of the River Action campaign group, welcomed calls to improve water quality monitoring.

“Other than at the minuscule number of designated river bathing water sites, nothing is being done to provide river users with even the most basic information on the dangers they are facing.

He said politicians should treat the report as a “major wake-up call, given the past failures to protect the public from the rising tide of sewage pollution”.

The engineers also suggested introducing incentives to members of the public to remove impervious surfaces in urban areas – like patios or paved-over gardens, which would help green cities too.

A Water UK spokesperson said: “There is an urgent need to invest in our water system. Water companies have a plan with proposals to double the current level of spending between now and 2030… Public health is a major part of the next phase of the programme, with bathing areas heavily prioritised for investment.”

The environment department (Defra) said it will consult later this year on new bathing water rules – though this may not be until after the general election.

They added: “Alongside the Environment Agency securing over £150m fines to date and quadrupling inspections, we are already driving the largest infrastructure programme in water company history of £60bn over 25 years, which will drastically reduce spills.”