About 600,000 British teachers and civil servants are set to join a rare nationwide strike today in the country’s biggest walkout since the coalition government took office last year.

Four trade unions voted to take action to protest against changes to pensions, in what one labour union warned could be the start of the most serious widespread industrial unrest in Britain since 1926.

Prime Minister David Cameron made a final effort on Tuesday to persuade them to abandon the strike, which will close or disrupt around 85 per cent of schools in England and Wales, as well as job centres, tax offices and courts.

He insisted the proposed changes to make public sector workers work longer and contribute more to their pensions were necessary but fair as Britain faced up to the challenges of an ageing population.

Cameron, leader of the centre-right Conservative Party which formed a coalition with the Liberal Democrats in May last year, also argued the strike was premature because talks between unions and ministers were still continuing.

“To those considering strike action, at a time when discussions are ongoing, I would say to you: these strikes are wrong – for you, for the people you serve, for the good of the country,” he said.

“It’s the changes we propose that are right.”

The reforms would raise the public sector retirement age by up to six years to 66, increase employee contributions by 50 per cent in some cases, and replace final salary pensions with one based on average career earnings.

Cameron insisted there was no option, warning that “the pension system is in danger of going broke”.

But there is widespread anger among public sector workers who have already been hit with a two-year pay freeze and face more than 330,000 job losses by 2015 as the government slashes spending to eliminate a record budget deficit.

Their frustration is underscored by the fact that today’s national walkout will be the first ever by Britain’s ATL education union in its 127-year history.

Some 78,000 of the school and college staff in the ATL are affected by the pensions changes, which it argues are unaffordable and could deter people from entering the profession.

About 220,000 members of the National Union of Teachers and 55,000 from the University and College Union have also been called out on strike, as have 250,000 civil servants in the Public and Commercial Services Union.

The unions are planning protests across the country, including in London, as well as picnics and breakfasts in solidarity with the strikers.

They are not being joined by Unison, the largest public sector union in Britain with 1.3 million members, which has opted to continue talking.

Unison general secretary Dave Prentis earlier this month warned of waves of industrial action by public sector workers. “It will be the biggest since the general strike (of 1926),” he told The Guardian.

Opposition Labour leader Ed Miliband has warned however that strikes “must always be the very last resort” and said the unions had yet to win the argument.

The government has also indicated it might tighten rules on when unions can call strikes, sparking comparisons with Conservative Prime Minister Margaret Thatcher’s reforms which hobbled the unions in the 1980s.

Since Thatcher’s time union membership has declined rapidly, and where one third of the workforce was unionised in 1995, this fell to just over a quarter in 2010.

Britain loses far fewer working days to strikes than the EU average, and the last major strike over pensions was in March 2006, by one million local government employees.

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