The Lib Dem Party authorities are concerned that the party will further go down in opinion polls as the result of protests against changes to the Disability Living Allowance. The government is planning to scrap the mobility element of the allowance for all recipients in council residential care from October 2012.

The move, leading to annual savings of £135 million, will have a direct impact on almost 80,000 people across the UK who are entitled by the allowance to buy electric wheelchairs and pay special transport costs. Thousands of people who are deprived of public transport because of their disabilities use the allowance of up to £49.85 per week to maintain their independence and quality of life, according to charities.

Bill Scott, of disability rights group Inclusion Scotland, said half of the £2 billion benefit cuts in Scotland would fall on disabled people. “The number of disabled people being plunged into relative or extreme poverty could be staggering. There is fear and anger out there,” he said. “Even people given lifetime allowance awards because their conditions will never improve will be reassessed. The government is redefining what it is to be a disabled person”.

The Lib Dem conference, on March 4 and 5, is threatening to turn into a financial headache for the party, because it must pay for a share of policing the extra demonstrators drawn by Clegg.

The protest will take place outside Perth Concert Hall on 4 March from 10.30am.