CAB manager, Jean Cheyne

The Citizens Advice Bureau (Cab) has already warned that, even if rises were capped at 12%, families on benefit will struggle to pay.

Jean Cheyne, manager of Glasgow Maryhill Cab told BBC Scotland: "If they are on a very low income or a benefit income it means cutting back on food or fuel, because there is nothing else that people on a low income can cut back on."

However, the water authorities have voiced their support for a �24m grant scheme being proposed by the Scottish Executive to help the worst off.

They have also announced that they are phasing out charitable relief on water charges over the next five years.

In the North of Scotland Water Authority (NoSWA) area, the total Band D bill for water and sewerage will increase by more than �50 to �350.18.

Chairman Colin Rennie said that meant the average household would face a 10p-a-day rise to 75p-a-day to pay for a massive investment programme.

Major investment

"The charges we are announcing today will pay for the latest step in the biggest investment in water and sewerage services in this part of Scotland since Victorian times," he said.

The authority needs to spend �500m on environmental measures and �400m on vital improvements to public water services over a six-year period.

Professor Alan Alexander

West of Scotland Water Authority chairman Professor Alan Alexander said charges in the area remained the lowest in Scotland, at �266.40 on Band D - an average of 55p-per-day.

The authority is planning to invest �1.1bn in essential work to maintain and improve services, including the rehabilitation of more than 1800 kilometres of mains - enough to stretch from Glasgow to Barcelona.

"We need to invest now to improve this infrastructure to secure the future of services to customers and improve public health," said Professor Alexander.

In the East of Scotland Water Authority area, the average Band D household will pay 74p per day - a rise of almost 12p a day to a total of �270.

'Realistic levels'

Chairman Robert Cairns said the authority would spend about �630m over the next five years on improvements.

"The only way we can make this investment is by charging customers at a realistic level that compares with water charges across the rest of the UK," he said.

Charities say that since no one is entirely exempt from water bills, those on lower incomes will be hit hardest.

The increases come against a background of under investment in the water industry.

European regulations make the improvement in standards a priority which requires immediate funding.