The three MEPs accuse the UK of not adhering to its obligations under multiple treaties including the main Brexit agreement and a UN charter.
Three French MEPs are calling on Brussels to take action against the UK after it allowed a significant amount of raw sewage to be dumped in the English Channel and the North Sea.
"We fear negative consequences on the quality of the marine waters we share with this country and incidentally on marine biodiversity but also on the activities of fishermen and shellfish farmers," the three MEPs wrote in their letter to Environment Commissioner Virginijus Sinkevičius on Wednesday.
Pierre Karleskind, Nathalie Loiseau and Stéphanie Yon-Courtin, all three from the centrist Renew group in the European Parliament, accused the UK of "exempting itself from environmental requirements" set out in EU legislation.
They also stressed that the UK has obligations under the EU–UK Trade and Cooperation Agreement -- a Brexit treaty -- and that it is a signatory of the United Nations Convention on the Law of the Sea.
"Despite this, the UK has chosen to lower its water quality standards. This is unacceptable and calls into question the efforts made by EU Member States over the last twenty years. The UK is committed to preserving the seas that surround it and that we share!," they wrote.
"We call on the Commission to use all political and legal means at its disposal to stop this situation," they added.
Last week, the UK's Environment Agency issued "do not swim" orders for over 20 beaches across the UK because of sewage discharge.
At fault were heavy rainfalls coming after a sustained period of dry weather which made the soil less able to absorb the rain and the water to reach the sewage network. In this case, sewage companies are allowed to dump so-called storm overflows into rivers and the sea to prevent flash floods in some areas.
This is expected to be exceptional with sewage companies meant to primarily discharge excess rainwater but some have accused them of dumping raw sewage as well.
In a joint opinion released in late June, Professor Chris Whitty, Chief Medical Officer for England, Jonson Cox, chair of Water Services Regulation Authority Ofwat, and Emma Howard Boyd, Environment Agency chair, flagged that data shows the use of storm overflows "is now not exceptional"
"In some cases, up to 200 discharges a year are occurring," they wrote. "This is obviously unacceptable on public health grounds."
They conceded that while the cost of ensuring that no discharge takes place may not be justified, reducing the frequency of discharges down to "genuine storms should however be a minimum expectation".
"It certainly is the expectation of the great majority of the public, including those who do not themselves use rivers recreationally as measured by polling data. Nobody wants a child to ingest human faeces," they added.
They nonetheless called on water companies to invest to boost the sewage system's resilience and capacity and improve river health, stressing that "we have 2 stretches of river in England and Wales with bathing water status. There are over 500 in France."
Learn more about