Water companies have been warned they face “consequences” if they do not look to put a stop to raw sewage being released into England’s rivers and seas.

MPs on Monday voted in favour of introducing tougher legal restrictions on the practice of releasing untreated waste into waterways via storm overflows after a Government concession was approved by 283 to 162 – a majority of 120.

The Commons result followed accusations by Labour of a “screeching U-turn” by ministers on their attitude to tackling sewage discharges after facing a public outcry when Tory MPs voted against stronger controls last month.

Ahead of the vote, environment minister Rebecca Pow said she had met water firms to “reiterate the action they must be taking to tackle storm overflows”.

Addressing MPs in Parliament, Ms Pow said the frequency of discharges was “absolutely unacceptable” and that water companies must rein in the practice or “face the consequences”.

She said the Government’s amendment – designed to “redraft” one put forward by the Duke of Wellington – would put a “direct legal duty” on water companies to secure a “progressive reduction in the adverse impact of discharges from their storm overflows”.

“If we do not see sufficient progress from water companies, Ofwat and the Government will be able to take enforcement action and we will not hesitate to do this,” said Ms Pow.

Sewage can be pumped out of the sewerage system and into rivers through combined sewer overflows – otherwise known as a storm overflow or release valve.

The overflows are designed to release excess water following heavy rain or a storm to stop sewage backing up into homes.

To stop this happening, water companies are allowed to release the rainwater and a smaller amount of untreated sewage into the country’s waterways.

The Environment Agency has reported that, in the past year, raw sewage was discharged into coastal waters and rivers in England more than 400,000 times, which Defra has branded “unacceptable”.

Environment Secretary George Eustice has previously said that the Government’s amendment that was approved by MPs on Monday was “mirroring” what peers had already voted for in the Lords.

The Duke of Wellington’s amendment to the Environment Bill would have placed a new legal duty on water companies to “take all reasonable steps” to prevent sewage discharges.

The duke’s amendment passed by a majority of 153 and the Bill was sent back to the Commons for further consideration. This enabled the Government to table its alternative concession following a fierce public backlash to it blocking a similar move on the green benches initially.

Shadow environment secretary Luke Pollard said ministers had been “shamed” into a U-turn on sewage but added the amendment did not go far enough.

The Labour MP said: “The amendment the minister has cited in lieu of the Duke of Wellington amendment is confined to storm overflows and not the sewage system as a whole.

“There’s no specific duty on Ofwat or the Environment Agency to ensure compliance – and there should be – and we need to have a focus on reduction on harm rather than adverse impacts.

“This looks like looking busy without making a real difference.”

Former Liberal Democrat leader Tim Farron said the change was designed to “get Conservative backbenchers off the hook” after many faced public ire for voting down stronger water controls.

He said: “There are no targets in terms of volume or in terms of timescale, in which case that leaves water companies with the power to continue what they do now.

“This is something to get Conservative backbenchers off the hook rather than to give water companies the direction that they need.”