The government has insisted water companies are responsible for reducing sewage discharges as Labour accused it of having its “head in the sand” over the state of Britain’s beaches.
Amid growing calls for ministers to clamp down on those contributing to pollution, Number 10 said it was the duty of firms to put customers before shareholders.
“We have been clear that the failure of water companies to adequately reduce sewage discharges is completely unacceptable,” a Downing Street spokeswoman said on Monday.
“They have a duty to put their customers before shareholders and we would expect them to take urgent action on this issue or face fines.”
The spokeswoman added: “We continue to speak regularly with them, the Environment Agency undertake enforcement action and monitoring, which we have stepped up.”
Downing Street said water companies were already facing legal action from regulators.
The spokeswoman said: “Since 2015 the Environment Agency has brought 48 prosecutions against water and sewerage companies, securing fines of over £137 million.”
She added that since privatisation the equivalent of £5 billion had been invested to upgrade water infrastructure but the companies must “continue to take action”.
But Sir Keir Starmer earlier accused the government of having its head in the sand over the scale of sewage being pumped into British waterways.
The Labour leader ministers had not been tough enough on water companies and had been cutting funding for the Environment Agency.
“I think there is huge anger about the sewage situation, because we’re seeing yet again sewage pumped into our rivers and into our seas,” he said.
“What it shows is that the government hasn’t been tough enough on the water companies and the enforcement against the water companies.
“Of course, at the same time they have been cutting money to the Environment Agency.
“We can’t go on like this with a government that knows there is a problem there, does absolutely nothing about it and it couldn’t come at a worse time.
“It is damaging our environment, but of course it is really affecting businesses at the height of the tourist season. Yet again, we say to the Government, get your head out of the sand and do something about it.”
Environment Agency data shows water companies are failing to monitor sewage discharges along the coastline including at British seaside resorts, according to analysis by the Liberal Democrats.
The party found that Event Duration Monitors (EDMs) used by firms across the UK either did not work for at least 90% of the time or had not been installed at all.
Environment spokesperson for the Lib Dems, Tim Farron MP, said: “These water companies could be guilty of gross negligence by failing to install sewage monitors.
“This is a national scandal and these new figures stink of a cover-up. Britain’s seaside resorts are being swamped by foul sewage yet the Government is nowhere to be found. Why on earth are Conservative ministers letting them get away with this?”
It comes after dozens of pollution warnings were issued for beaches and swimming spots in England and Wales following heavy rain that overwhelmed the sewage system.
There has been growing public outrage in recent years at the volume of raw or partially treated sewage pumped into the UK’s rivers and coastal waters.
Water firms are being criticised for not investing money back into the UK’s outdated water infrastructure, with mounting pressure on ministers to intervene.
In a report published in July, the Environment Agency said water company bosses should face jail for the worst pollution incidents, describing the sector’s performance in 2021 as the “worst we have seen for years”.