Labour wants all water companies to make clear help available to bring down bills amid claims that the Government is failing to stand up to the industry.
The Opposition will today table amendments to the Water Bill to ensure hard-pressed households are not missing out on discounts.
At £499, South West Water's average annual charge is the highest in the country thanks to botched 1980s privatisation. Bill payers in London on average pay £150 less.
It was the reason why the Government has given a £50-a-year subsidy to all households in the region. But many families in Devon and Cornwall pay more than £1,000 a year.
Labour's amendments, to be debated in the committee of the House of Commons scrutinising the legislation, would require water companies to provide all customers with details of schemes to help with the cost of water alongside their bills, with clear information about how to apply, to tackle the lack of awareness of help available.
It would also bring about a new national affordability Scheme to help those struggling to pay their water bill, replacing the current voluntary arrangement which has seen just three water companies – including South West Water – establish a "social tariff".
The amendment would also provide the Consumer Council for Water with new powers of redress to resolve customer complaints, including the ability to require water companies to make refunds, and new rights for it to be consulted on the charging schemes of water companies.
Water companies would also be forced to submit to Government annual information regarding their performance, investment, taxation structure, corporate structure and total amount of dividends paid to shareholders, and enable Ofwat to use this information to reopen price settlements to reduce bills.
Maria Eagle MP, Labour's Shadow Environment Secretary, said: "The rising cost of water is adding to the cost of living crisis, yet the Government refuses to stand up to the water companies despite many walking away with hundreds of millions of pounds and paying little tax.
"David Cameron's weak response has been a single letter begging the water companies not to hike bills too much, even though he could force them to act by using his own legislation."