The government's new plan to crack down on sewage discharge by 2050 has been branded a "cruel joke" and "licence to pump sewage on to our beaches".
The Department for the Environment (DEFRA) said on Friday that water companies will have to deliver £56bn of capital investment over the next 25 years to stop untreated sewage spilling into the UK's seas and rivers.
There have been growing calls to strip water company bosses of their multimillion-pound bonuses after outrage at how much sewage is being pumped into the sea.
Under the plan, firms will have until 2035 to improve how they manage all the sewage overflows discharging next to bathing water, and improve 75% of the overflows at top nature sites. By 2050, this will apply to all waterways.
The government said it was introducing the "strictest ever targets" to crack down on sewage spills.
But the Lib Dems branded the plan a "cruel joke" and claimed it will result in 325,000 sewage dumps a year by 2030.
The party's environmental spokesman, Tim Farron, said: "This government plan is a licence to pump sewage on to our beaches and in our treasured rivers and lakes.
"By the time these flimsy targets come into effect, our beaches would have been pumped full of disgusting sewage, more otters will be poisoned and our children will still be swimming in dangerous water."
The party claimed the plan will result in tax payers largely paying for the improvements, despite water company bosses earning huge bonuses in recent years.
Previous analysis by the party found the average water company executive bonus rose by a fifth (18%) last year and that the average water company exec annual bonus now stands at £670,000.
The document published by DEFRA said there will be no bill impacts until 2025, but it is estimated that annual bills over the whole period to 2050 would eventually rise by £42 compared to current prices.
It comes at a time when households are already feeling the crunch with energy bills due to soar for millions in October following a record 80% increase in the price cap.
'The whole thing stinks'
Mr Farron slammed the decision not to ban water company chief executive bonuses.
"Whilst they roll in the cash, we swim in sewage. The whole thing stinks," he said.
"On the day when this cost of living crisis hit catastrophe levels, the government has snuck out this news. They have taken the concept of 'put out your trash' to a whole new level."
Ministers have been facing growing calls to crack down on water companies for failing to invest in the UK's outdated water infrastructure.
Dozens of pollution warnings have been issued for beaches and swimming spots in England and Wales this week following heavy rain that overwhelmed the sewage system.
Untreated sewage water was spotted pouring into the sea near Bexhill, East Sussex, on Wednesday, while on Thursday, French MEPs accused the UK of putting fishermen's livelihoods and public health at risk by pushing sewage into the English Channel.
The government said water companies will have to achieve a number of targets so that discharges only happen when there is unusually heavy rain and when there is no immediate adverse impact to the local environment.
DEFRA said companies that do not meet its targets will have to refund customers or face fines, stressing that companies cannot profit from environmental damage.
Environment Secretary George Eustice claimed the UK government is "the first government to take action to end the environmental damage caused by sewage spills".
He said: "We will require water companies to protect everyone who uses our water for recreation, and ensure storm overflows pose no threat to the environment.
"Water companies will need to invest to stop unacceptable sewage spills so our rivers and coastlines can have greater protection than ever before."
'Conservatives have taken-up writing fiction'
However, Labour accused the government of "writing fiction".
Jim McMahon, Labour's shadow secretary of state for environment, said that based on last year's figures, the "weak improvement targets" will result in another 4.8 million sewage spill events in the UK between now and 2035.
"Britain deserves better than a zombie Tory government that is happy for our country to be treated as an open sewer," he said.
"Labour will use the levers of power to hold reckless water bosses to account legally and financially, and toughen regulations to prevent them from gaming the system."
DEFRA said it will review its plan in 2027 to assess "where we can go further".