Tory MPs have been defending themselves from accusations they have given the go-ahead to water companies to dump raw sewage in rivers.
A proposal from the Lords to the Environment Bill that would have placed legal duties on the companies to reduce discharges was defeated by 265 MPs' votes to 202 last week.
The MPs say safeguards already exist and new measures would cost billions.
Critics say the UK is "lecturing" the world while its rivers are polluted.
With just over a week to go until the UK hosts the COP26 climate summit, there is intense focus on ministers' green credentials.
Last Wednesday, 265 MPs voted with the government to reject an attempt by the House of Lords to toughen up the approach to the discharge of sewage, while 22 Conservative MPs rebelled and voted against the government.
The move has sparked an uproar on social media.
Peers had tabled an amendment to the Environment Bill that would have forced water companies and the government to demonstrate progressive reductions in discharges of untreated sewage and required them to "take all reasonable steps" to avoid using combined sewer overflows.
But ministers said the changes were unnecessary because safeguards are already contained in the bill.
'Every river polluted'
Speaking on Radio 4's Today programme, former singer Fergal Sharkey, who now campaigns to clean up the nation's waterways, said it was a "disgrace".
"We're lecturing the rest of the planet on climate change yet the reality is there is not a single river in England that makes good overall environmental health," he said.
He said "every single river" in England is polluted and "a major cause is the water industry dumping sewage".
He added: "The truth is what we are looking at is the result of a massive under-investment in infrastructure for the last 30 years and a complete failure of oversight and regulation of the industry by Ofwat, the environment agency and the government itself."
He said ministers were "unwilling and incapable" of dealing with the situation.
Conservative Huw Merriman, who voted against the government and for the amendment, said "what was being proposed by the government wasn't enough" and he hoped ministers would "be persuaded" it was the right way to go.
He said: "To have sewage being discharged down streets, when there is too much rain, into the sea" is "just absolutely shocking".
"It does mean more investment. That may ultimately mean more expensive bills, but we're talking about decades of investment and it's got to happen," he said.
Unfair to taxpayers
But fellow Conservative, Julie Marson, who voted against the amendment, said "there is a lot of misinformation floating about" on the issue and while the proposal itself was "sound", its "fundamental flaw" was that it "had no plan as to how this can be delivered and no impact assessment whatsoever".
She wrote: "The preliminary cost of the required infrastructure change was estimated to be between £150bn and £650bn.
"Unless we asked taxpayers to contribute, most of the water companies who would be carrying out this work would go bankrupt, meaning the work could not be completed anyway.
"The cost works out at between about £5,000 and £20,000 per household.
"I felt it would be unfair to sting local people with a bill of this size."
She said the existing legislation already placed a new duty on water companies to continuously monitor the water quality upstream and downstream of a storm overflow and of sewage disposal works.
Another Conservative, Fay Jones, tweeted that the criticisms of MPs were "deeply misleading".
She wrote: "It ignores the massive flaw in the amendment (i.e forcing taxpayers to pay up to £600bn to dig up Victorian sewerage system) and the work the government is already doing to reduce discharge from storm overflows."
And Conservative, John Howell, said in a statement he voted against the amendment because "it is necessary to be realistic" given the age of the sewerage systems and the potential disruption to homes and businesses.
The accusation that he voted to allow water companies to pump raw sewage into rivers "is far from the truth", he said.
"It would be just as fair to say that Liberal Democrat and Labour MPs voted to pump raw sewage into your home given that resolving the problem by their half-baked proposal of sewage discharges would require rebuilding the sewage system and could cost up to £600bn and take many years," he added.
Scale of problem
Water companies discharged raw sewage into rivers in England more than 400,000 times last year, according to figures published by the Environment Agency.
Untreated effluent, including human waste, wet wipes and condoms, was released into waterways for more than three million hours in 2020.
The Environment Agency allows water utilities to release sewage into rivers and streams after extreme weather events such as prolonged heavy rain.
This protects properties from flooding and prevents sewage from backing up into streets and homes.
The agency says that overflows are "not a sign that the system is faulty", and that they are "a necessary part of the existing sewerage system".
A government spokesperson said the amount of sewage discharge by water companies into rivers was "not acceptable".
The spokesman added: "We have made it crystal clear to water companies that they must significantly reduce sewage discharges from storm overflows as a priority.
"If we do not start to see significant improvements, we will not hesitate to take action through the new measures directly on water companies in the Environment Bill.
"We have provided over £3bn of investment to tackle pollution in rivers and we expect to see results."
The Environment Bill will return to the Lords on Tuesday, where peers are expected to re-insert the measures before it goes back to the House of Commons later this week.