Monitors being used for measuring the amount of sewage being pumped into the sea across the UK are faulty or not even installed, the Liberal Democrats have said.

Environment Agency data shows water companies are failing to monitor sewage discharges along the coastline including at British seaside resorts, according to the party’s analysis.

It comes as dozens of pollution warnings were put in place across beaches and swimming spots in England and Wales this week after heavy rain overwhelmed sewer systems, leading water companies to release sewage into the natural environment.

Ministers are facing growing calls to clamp down on the water firms who are being criticised for not investing money back into the UK’s outdated water infrastructure.

Boris Johnson’s father Stanley blamed his son’s administration for the sewage problem.

In an interview with the Prime Minister’s sister Rachel Johnson on LBC radio, Stanley Johnson said: “We have to blame the Government for not pressing this matter as hard as it should’ve done.

“Absent the EU push as well, you can understand how the Government felt able to not push this thing as it should’ve pushed.”

The Liberal Democrats said water companies have either installed Event Duration Monitors (EDMs) – devices which measure the number and length of sewage dumps from storm overflows – that do not work 90% of the time or have not been installed at all.

The party found that 1,802 monitors installed by water companies across the UK did not work for at least 90% of the time, while there were no monitors installed during 1,717 storm overflows.

In total, 24% of sewage discharges went unmonitored last year, it said.

Anglian Water has the highest rate of failure, with 49% of all its sewage discharges not measured due to faulty or no monitors installed, according to the party.

This is followed by South West Water with 30% and Severn Trent Water with 29%.

One in eight of South West Water’s sewage monitors installed at designated bathing locations across Cornwall and Devon are either faulty or not installed, the party said.

In Sussex, Southern Water was found to have altogether failed to install one at the popular seaside spot of Littlehampton Pier while one in Seaford was working only a third of the time.

It comes after a previous analysis by the Liberal Democrats found water companies dumped sewage in public swimming spots for more than 160,000 hours last year.

The Labour Party earlier this week said figures it obtained from the Environment Agency through Freedom of Information requests showed raw sewage has been pumped into UK waterways for a total of 9,427,355 hours since 2016.

The party also said the data shows a 2,553% increase in the number of monitored discharge hours between 2016 and 2021, arguing the situation is “drastically worsening” under the Conservatives.

In light of the latest analysis on monitors, the Liberal Democrats say the amount of sewage could be “dramatically higher”.

The party’s environment spokesperson, 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?

“Sussex has been devastated in recent days by disgraceful sewage dumps because of Southern Water.

“The CEO of Southern Water should go to Seaford to check on this sewage monitor immediately.

“The public needs to know how safe, if at all, popular beaches are for swimming.”

In response to the issue, the Department for Environment, Food and Rural Affairs released a response earlier this week outlining the action it is taking.

Water minister Steve Double said: “We are the first government to take action to tackle sewage overflows.

“We have been clear that water companies’ reliance on overflows is unacceptable and they must significantly reduce how much sewage they discharge as a priority.

“This is on top of ambitious action we have already taken including consulting on targets to improve water quality which will act as a powerful tool to deliver cleaner water, pushing all water companies to go further and faster to fix overflows.

“Work on tackling sewage overflows continues at pace and we will publish our plan in line with the 1 September statutory deadline.”

An Anglian Water spokesperson said: “Following over £300 million of investment in the last decade, all but three of the places designated for bathing in our region are rated as good or excellent for bathing water quality, and all have EDM monitors installed on them.

“Work to install EDM monitors on all the CSOs (combined sewer overflows) across our region is ahead of target as part of our Water Industry National Environment Programme as agreed with the Environment Agency.

“We will have full coverage across all CSOs by the end of 2023.”

The PA news agency has also contacted Southern Water, South West Water and Severn Trent Water for comment.