A committee of MPs has warned some pensioners could have to spend 11 per cent of their income on water.

In a new report released on Wednesday, the Commons environment, food and rural affairs committee warned water price rises are hitting the poorest households hardest.

The report also highlighted regional disparities in prices between different suppliers.

Customers in South West England are facing the biggest increases in their bills even though they already pay the most.

The MPs estimate the average bill in the region could rise from £357 now to £418 in 2009/10.

That would mean some pensioners paying more than one tenth of their disposable income on water and sewerage.

In contrast ministers argue no more than three per cent should be spent on water charges.

Committee chairman Michael Jack said the government should rethink its approach to regulating the industry.

"The further rise in water bills over the next five years flags up the growing challenge of water affordability for Britain's low income families," he said.

"In dealing with this challenge, the government will also have to consider carefully the growing cost to water users of further environmental legislation, the effects of climate change and whether a five-year pricing cycle is the best way to deal with this problem."