Pensioners' groups are being asked to back the petition

Help the Aged said council tax bills had increased by 80% since 1993 - twice the rise in the state pension.

Its petition will urge ministers to set up an expert body to examine the fairness of the existing system and look at the viability of replacements.

The Scottish Executive said it was committed to reviewing the tax.

A spokesman said the partnership agreement struck after last year's election contained a promise to review local government finance - and that the council tax would form part of that process.

Local authorities north of the border are preparing to set their bills for 2004/2005 next week.

Deputy Environment Minister Allan Wilson announced details of water charges - which will fall by 3.4% for customers in the north of Scotland but rise by 5.1% in the east and west - on Tuesday.

Pensioners south of the border have already shown their opposition to the current system.

Last month a 35,000-strong petition calling for an end to the tax was handed in to Downing Street.

The forthcoming review of local government finance provides the perfect forum to consider how the system could be improved Stuart Hay Help the Aged

Help the Aged's Scottish petition, which will be officially launched later this month, is seeking the support of major pensioners' groups across the country.

The petition will say that pensioners are being "unfairly discriminated against" under the council tax compared with other households.

It calls for the establishment of an independent expert body, as part of the review of local government finance, to consider the fairness of the existing tax and possible replacements.

The aim is to submit the document to Holyrood's petitions committee.

A report for Help the Aged suggested that the council tax had risen by 80% in Scotland in the decade since its introduction in 1993.

In the same period, the basic state pension rose by 40%.

Tax on income

The rise in charges topped 90% if water and sewerage bills were added into the equation, the report found.

Last year's average 3.9% increase in council tax bills across Scotland compared with a 2.5% rise in pensions.

Stuart Hay, Help the Aged's policy and parliamentary officer, said that the average council tax bill was equivalent to 25.5% of the state pension - compared with less than 4% of gross annual earnings.

Figures for 2001/2002 suggested that council tax bills accounted for 5% of pensioner households' income, compared with 3% for non-pensioner households.

Council tax bills have risen faster than pensions

Mr Hay said: "This has the same impact as making pensioners pay 2p tax on their income."

Research suggested that the take-up rate for council tax benefits was about 65% among pensioners, falling to 45% among those who owned their own homes.

Mr Hay said that meant that up to 148,000 pensioners may not be receiving what they are entitled to - which could add up to �58.5m in lost benefits.

"The forthcoming review of local government finance provides the perfect forum to consider how the system could be improved or whether there is a case for comprehensive reform or introducing new forms of taxation," he said.

The IsItFair campaign is also organising a petition in Scotland, calling for the scrapping of the council tax.

Range of issues

An executive spokesman said a commitment had been given to review local government finance.

"That will take a look at a whole range of issues, including the council tax," he said.

It is expected that the review will look at alternatives to the council tax, in addition to the existing system.