Peers have forced a climbdown by the Government over the dumping of raw sewage in rivers and the sea.

The House of Lords today backed by 213 votes to 60 a proposal to place a new legal duty on water companies to "take all reasonable steps" to prevent sewage discharges.

This will enable the Environment Bill to be sent back to the Commons where the Government will table its own amendment.

The Department for Environment, Food and Rural Affairs (Defra) has now pledged that in the new amendmnent the bill will be "further strengthened".

It says it will put in place a 'duty enshrined in law' to ensure water companies 'secure a progressive reduction in the adverse impacts of discharges from storm overflows'.

Defra's climbdown came only hours after Downing Street - and York Outer MP Julian Sturdy - had defended the decision last week to vote against the original amendment to the bill, which aimed to force water companies to reduce the amount of raw sewage pumped into waterways.

The Prime Minister's official spokesman said then that it was "not right to sign a blank cheque on behalf of customers" after the Government put the cost of delivering on the terms of the Commons amendment at more than £150 billion.

Mr Sturdy, meanwhile, defended his decision to vote against the amendment by saying it would have transferred "unlimited costs for cutting discharges right onto local residents".

And he accused campaigners who criticised the decision of 'misrepresenting' the vote, and using it as a basis for 'fear-mongering and demonisation of MPs'.

Following the Government climbdown today, Environment Secretary George Eustice warned that strengthening measures to force water companies to reduce raw sewage finding its way into river systems would lead to rising household water bills.

In comments to broadcasters, he said that the water sector would have five years to show progress on the matter, but that bills would have to increase to fund infrastructure improvements.

He said: "We've been very clear that we want to see a reduction in these storm overflows over the next five-year period of the water pricing plan.

"That will need to be funded and will lead to some increases in water bills to fund that."

Speaking earlier today, York Central MP Rachael Maskell, who voted in favour of the original amendments, said the lack of investment in creaking sewage and waste water systems was a 'scandal' - and that raw sewage in York's rivers, as seen in the Foss over the summer, was a health hazard.

"We know that the rivers flood in York, so that sewage could end up in people's homes, causing disease and sickness," she said.

"The water companies have not acted, so we need legislation to force change."

A spokesman for Yorkshire Water said making improvements in river quality was a 'key priority' in the company's future plans.

But he added: "It is vital regulators take steps to enable increased investment in the infrastructure required to deliver on our aims.”

Why is cleaning up our sewage system so difficult?

The key problem with our antiquated sewage system, some of which dates back to Victorian times, is 'combined sewers', which carry both sewage from homes and businesses and rainwater from pavements and roads.

Normally these can cope - but following exceptionally heavy rainfall they can get backed up. 'Storm overflow' areas capture the overflows, and allow solid sewage to settle at the bottom. But diluted waste water, including some sewage, is still sometimes discharged into rivers.

Many storm overflows have 'preliminary treatment' such as screens or storm settlement before any discharge is made, Yorkshire Water says.

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