As the first national postal strike in seven years looms, a Stirling University industrial relations expert says his research shows the UK has the most militant postal workers in western countries.
Gregor Gall, reader in Stirling's department of management and organisation, said the UK differed from comparable countries in not having privatised postal services.
"Because they're not in the private sector, there's a greater confidence on the part of postal workers to be able to stand up and put forward their demands," he said. "They don't fear private competition in the same way as postal workers elsewhere."
Dr Gall has compared Britain's postal workers with workers in nine other industrial countries, including France, Germany and Sweden. He found the shift from the postal service being a state organisation to a private company competing with other carriers had reduced unions' power.
But there were no indications that the UK was heading towards privatisation, as the Conservative government's attempts foundered over the "social significance" attached to the Royal Mail.
"The argument was that (postal workers) provided a national service that was part of the fabric of society, with it costing the same to send a letter to John O'Groats from Edinburgh as to somewhere else in Edinburgh."
Dr Gall, who this summer published a book, The Meaning of Militancy? Postal Workers and Industrial Relations , examining industrial relations in the Royal Mail since the early 1980s, said militancy was also stronger because of the postal workers' system of national and workplace bargaining.
Local shop stewards negotiated elements of pay and conditions, and the leadership was responding to local pressure from members for higher pay.