Picket lines have been mounted outside schools, council buildings, job centres and courts across Bury by striking public sector workers in the biggest outbreak of industrial unrest since the coalition was formed.

Union leaders said early indications were that the 24-hour walkout was being strongly supported.

It has forced the closure of 78 schools in Bury and caused disruption to the courts, government services and travel from Manchester airport.

Members of the National Union of Teachers (NUT), Association of Teachers and Lecturers (ATL), University and College Union and the Public and Commercial Services union (PCS) went on strike in a bitter row over plans to increase their pension contributions and raise the retirement age.

The PCS said it was encouraged by support from its members and announced that it had recruited 2,000 extra members in the past few weeks.

"We are expecting the best supported strike we have ever seen," said one official.

Cabinet Office minister Francis Maude said teachers "absolutely don't" have to strike, and should not because talks are still ongoing, with another meeting between the Government and trade unions due next week.

He told BBC Breakfast: "It's absolutely unjustifiable for parents up and down the country to be inconvenienced like this, forced to lose a day's work when they're trying to go out to work to earn money to pay taxes that are going to support teachers' pensions, which will still, at the end of this, be among the very best pensions available."

Among the buildings being picketed was Parliament, with strikers saying they hoped some left-wing MPs would refuse to cross. Strikers also picketed the Royal Courts of Justice in central London and many courts including Westminster magistrates.

Unions were also targeting the headquarters of the education and business departments. Immigration officers at ports and airports across the UK joined the strike, with the prospect of long delays for travellers returning to the country.

Police leave has been cancelled in London, where union leaders and thousands of activists will take part in a march, followed by a lunchtime rally in Westminster.