A union-backed convoy of Queensland truck drivers is on its way to Sydney as part of a mass protest highlighting the danger of unreasonable deadlines.

The Transport Workers Union (TWU) will stage a demonstration with hundreds of members when delegates from Queensland and South Australia arrive in Sydney on Thursday.

The union has taken issue with Coles in particular, accusing it of forcing drivers to operate in an unsafe environment by setting unrealistic deadlines.

TWU Queensland secretary Peter Biagini concedes that supermarkets and other major retailers do not actually employ the trucks or drivers themselves, he claims that they put pressure on transport firms to hold unsafe standards to win contracts.

“For them to survive they've got to bow to their clients, which means cutting back on maintenance, pushing the drivers and making sure that the wheels are turning 24 hours, seven days a week,” Mr Biagini told AAP reporters.

Mr Biagini wants big retailers to work with the industry on a “sustainable” standard for truck drivers, and to acknowledge the risks that cost-cutting measures can bring.

But Coles does nto appear to be coming to the table.

The supermarket giant has slammed the union for its “deliberately misleading” claims about road safety.

“Coles does not employ any truck drivers. It contracts the services of market-leading logistics providers such as Toll and Linfox,” it said in a statement.

“Like Coles, these companies put enormous effort into safety measures for their employees and employee safety is their priority.”

Coles denied the TWU’s claims that it gave donations to political parties, and also cited analysis by Deloitte that showed it accounts for just 0.8 per cent of the national road freight task.