The fight to reduce sky-high water bills in the Westcountry will be an "uphill struggle", an MP has warned as an inquiry is launched into tackling affordability.

An Environment, Food and Rural Affairs (Efra) select committee has called for evidence to examine whether South West Water customers are paying too much for water and sewage.

But Tiverton and Honiton MP Neil Parish, who sits on the Efra scrutiny panel, has warned that civil servants have already shown "resistance" to calls for a national levy to keep Devon and Cornwall's beaches clean.

Among a series of recommendations, the independent Walker review last year suggested households elsewhere in the country should help take the strain placed on the region by the flood of tourists each year.

A White Paper is expected to be published by June next year on the threat of future water shortages and flooding as well as water bill charges.

While it could pave the way for cheaper bills, there is no certainty that it will consider the Westcountry's beaches to be a "national asset" and that the whole country should, therefore, pay for their upkeep.

Tory MP Mr Parish said that the inquiry was an opportunity to make the point that South West Water bill payers are forking out about £150 more a year than the national average.

He said: "We would like a national levy, but we have met quite a lot of resistance to that, although we reckon it would only mean an extra £1.50 to £2 per bill nationally. It is still an uphill struggle, but there is a chance."

A central Government grant to help the poorest households was another suggestion to fall out of the Walker review. But commentators argue that this would do little for the vast majority of hard-pressed households in the region.

In the summer of 2008, Prime Minister David Cameron, then leader of the Opposition, acknowledged the "unfairness" of soaring bills in the region.

"I understand the unfairness that people feel in the South West that they are paying a lot of money so that there are clean beaches for people like me from Oxfordshire to come and play on," he told an audience of WMN readers.

Westcountry householders have significantly higher bills than anywhere else in the country – an average £490 compared to £343.

The main cause is that residents are paying for the clean-up of nearly a third of the country's coastline.

The select committee has invited all interested parties to submit evidence in writing by October 7.