Help the Aged is lobbying a Holyrood committee

Help the Aged said 70% of those who took part in a survey fell into that category as their bills accounted for at least 10% of their income.

More than 50% said they had been forced to cut their budgets for things like food and heating to afford tax rises.

The organisation, which sent the survey to 1,000 people, wants the Scottish Executive to find out the real figure.

A report based on the survey has been submitted to the local government finance review committee.

Members of Older Peoples' Forums across Scotland were asked how council tax and water rates increases had affected their lifestyles.

Our findings have alarmed us, and we are now worried that hundreds of thousands of Scottish pensioners could be living in council tax poverty Richard Meade Help the Aged

On average, these charges accounted for 13% of their net income.

Help the Aged said that council tax benefit provided a "welcome relief" for some people.

But it said: "A large number of pensioners entitled to the benefit do not claim it, mainly due to a lack of awareness and long, complicated forms."

Scottish policy and parliamentary affairs officer Richard Meade said: "Our findings have alarmed us, and we are now worried that hundreds of thousands of Scottish pensioners could be living in council tax poverty."

Help the Aged has produced thousands of postcards urging members of the Holyrood committee to consider the impact on pensioners when making its recommendations to the executive.

These will be distributed to older people, who will be asked to send them to the committee.

The Conservatives accused Labour of failing pensioners and pledged to restore the link between pensions and earnings.