Plans to take tougher action against water companies for pumping sewage into rivers and the sea will once again be opposed by the government, Downing Street has announced. The prime minister’s spokesperson confirmed the government would retain its resistance to adopting an amendment to the environment bill tabled by the Duke of Wellington, which was passed by the Lords earlier this month but subsequently rejected by the Commons. A standoff is expected to resume on Tuesday when peers vote again on the amendment and are likely to pass it, triggering parliamentary “ping-pong” between the upper and lower chambers. Ministers are wary of the huge public backlash to their stance, and there are suggestions some form of compromise solution could be offered if the Lords passes the amendment for a second time. A total of 22 Tory MPs rebelled to support it last week, and some of them expect that figure to rise at the next Commons vote given that many more abstained. One Conservative said the government was “shitting themselves” about the furore. On Tuesday, Boris Johnson’s spokesperson criticised the current “failure of water companies to adequately reduce sewage discharges is unacceptable” and said it sympathised with the intentions of the amendment. However, he said the cost of forcing water companies to “take all reasonable steps to ensure untreated sewage is not discharged from storm overflows” had not been estimated – warning it could be up to £150bn. He added: “That would mean that individuals, every one of us, taxpayers, paying potentially thousands of pounds each as a result so it’s not right to sign a blank check on behalf of customers without understanding the trade-offs and the bills that would be involved.” After a photographer released footage of untreated sewage being released into a harbour in Hampshire for 49 hours straight, Labour said the government was to blame for letting water companies get away with it and urged ministers to support the amendment. “People are right to be upset at the dreadful state of England’s rivers,” said Luke Pollard, the shadow environment secretary. “Not one English river is in a healthy condition and there has been zero improvement since 2016.” He added: “The Conservatives should urgently U-turn on their decision to block the environment bill amendment so that water companies are forced to reduce the amount of sewage they pump into our rivers and seas. The millions which go to shareholders do nothing to help with cleaning up our rivers and seas.” The environment department said that completely eliminating sewage disposal resulting from storm overflows would be extremely challenging given “the age of our sewerage systems”. It added there would be new duties on water companies to monitor water quality, come up with a plan for developing systems to decrease the amount of sewage discharged over the next 25 years, and provide real-time information on storm overflows.