Labour has promised a crackdown on water bill dodgers to fund a discount for the poorest families, conference has heard.
Mary Creagh, Shadow Environment Secretary, said a Labour government would attempt to claw back the £15-a-year added to every household's water charge by those refusing to pay.
The money would then be used to underwrite a cut for hard-pressed bill payers under so-called "social tariffs".
She went on that Labour would insist that all water companies offered discounts to the worst off. At present, firms are under no obligation to provide deals for families in need.
South West Water bill payers still suffer from the highest charges in the region despite the Government's £50 annual discount for every household from next April.
Mrs Creagh told delegates: "People are struggling to pay their water bills. Bad debt adds £15 a year to everyone's bill.
"We want water companies to cut that bad debt by taking tough action on those who won't pay in order to help those who can't pay.
"A Labour Government would force all water companies to offer social tariffs to help those most in need. But this Government wants to leave it to water companies to decide for themselves."
South West Water's average levy went up by £26 to £543 this year – the highest in the country and £167 more than the national average.
In June, the Government has issued guidance to water firms to create "social tariffs".
The document suggested water companies should push up prices for households not benefiting from the reduction by up to 1.5% to fund the discount. This would equate to adding £8 to the average South West Water bill.
The firm, which provides water and sewerage to 700,000 homes in the region, is looking at several options for a new company social tariff.
A committee of MPs this year found there is a "significant proportion" of bad debt in the water industry accrued by those who simply "won't pay", principally in the rental sector, where 80% of water debt can be found.
Unlike electricity and gas providers, no water company can disconnect supply to people's homes, on public health grounds. The Government has ruled out giving water companies this power.
Ministers are consulting on measures to reduce bad debt but Labour, in early proposals, think it could give water regulator Ofwat more powers to insists companies do more to tackle the problem.
The water industry wrote off £328 million of household debt in 2010-11. The cost amounts to nearly 4% of the average water bill.
Meanwhile, Mrs Creagh criticised the Conservative and Lib Dem coalition for being "out of touch" with rural communities – pointing to the plan to abolish the Agricultural Wages Board, which sets pay and conditions for thousands of Westcountry farm workers.
She said Labour had managed to delay legislation to scrap the body, meaning 23,460 rural workers had been given a pay rise yesterday that they would otherwise have missed out on.
"Next year, if the Tories have their way, they won't," she said.
"And when the AWB goes rural wages, over time, will sink to the legal minimum. The government's own assessment shows that the rural high street will lose £9 million a year as those workers lose their sick pay and holiday pay.
"But I promise you that I will be working with my shadow team to expose how out of touch the Tories and Lib Dems are with rural areas."
She concluded: "Labour has changed. Let's show people we are the change the country needs."