The government has launched a defensive social media campaign after MPs faced anger from their constituents over last week’s sewage vote, in which an amendment to the environment bill that would have placed a legal duty on water companies not to pump waste into rivers was voted down. Many Conservative MPs posted almost identical statements on Monday morning after a weekend of anger over the vote. Government sources confirmed to the Guardian that the information in these posts had been supplied by No 10. MPs including Steve Brine, Ben Everitt, Michael Fabricant, Anne Marie Morris and Sally-Ann Hart published similar “explainers” about the vote on their websites. They argue that the amendment did not include an impact assessment, and the costs incurred by immediately banning sewage spills would be too great. The statement reads: “To eliminate storm overflows means transforming the entire Victorian sewage system to a whole new sewage system. It would be irresponsible for any government to spend an estimated preliminary cost of anywhere between £150bn to £650bn to transform the entire sewage system. This is a huge amount to spend in an ordinary time, let alone at a time of a continuing health pandemic. “To give some perspective, £150bn is more than the entire schools, policing and defence budget put together and £650bn is billions more than we have spent on supporting livelihoods and jobs throughout the health pandemic.” Only 22 Conservatives rebelled against the government last week, after the environment secretary, George Eustice, recommended that MPs vote against the amendment. Martin Salter, the chief policy adviser of the Angling Trust, said: “We know from the unconvincing, identikit replies received by our members that government MPs had been instructed to issue with a standard response to constituents which avoided the question of taking action to combat sewage pollution in favour of yet more endless monitoring. “There is clearly going to be a battle between the Lords and Commons on this important issue and we intend to keep up the pressure for as long as we can. “Our rivers are badly polluted and cannot wait for more plans and reports. It seriously questions the government’s commitments to leaving the environment in a better state than when they took office.” A widespread social media campaign involved constituents posting photographs of their MPs online and asking why they voted against the amendment. The former Undertones singer Feargal Sharkey, who has been a driving force behind the campaign, was vying for a rather different number one as he rallied his fans on Twitter to keep putting pressure on their MPs. He said: “Currently trending at Number 3 in the UK is #Sewage. Let’s make it Number 1.” Joan Edwards, the director of policy and public affairs for the Wildlife Trusts, said: “Our rivers and seas are the bedrock of our biodiversity. But, chemicals, sewage and manure continue to pour almost unabated into our already polluted waterways. It is disappointing therefore that the government removed an amendment to the environment bill that would have placed a legal duty on water companies to reduce harm caused by sewage discharges.” There has been consternation inside government at the way the vote on the amendment last week has been portrayed, with insiders insisting that if the measures had been adopted they would have added a huge cost to water companies that would then have seen them write a “blank cheque” to pass on to consumers. One Tory MP said the size of the rebellion last week had also caused concern, and the government was – ironically – “shitting themselves”. The rebellion could grow further if Conservative backbenchers who abstained last time switched to supporting the amendment when it is likely to be reintroduced by the Lords on Tuesday. A government source said they would not accept the same amendment because it would have huge implications – including potentially digging up people’s homes and businesses – but signalled they were open to further compromise. They said: “Our door is very much open. We’re willing and ready to engage and are doing a lot of work in this area.” The health minister Maria Caulfield criticised those who were lobbying their MPs on social media. She said: “None of us voted to discharge sewage into the sea and those of who have spread lies and misinformation should hang their heads in shame. Don’t ask why MPs get death threats if you have been part of this today #toxic.” The vote came seven weeks after wastewater plants were given permission by the government to dispose of sewage not fully treated because of a shortage of chemicals resulting from a lack of HGV drivers. The sewage measure, introduced in the Lords by the Duke of Wellington, is due to return to the upper house on Tuesday, where it is expected to be sent back to the Commons for another vote by MPs. There were 403,171 spills of sewage into England’s rivers and seas in 2020, according to the Environment Agency, adding up to over 3.1m hours of spillages.