London: British public sector workers on Thursday began a one-day strike which was expected to disrupt schools, airports and ports in the biggest walkout since the government took office last year.
Prime Minister David Cameron said the estimated 600,000 teachers and civil servants who were expected to join in the strike over proposed pension reforms were acting unreasonably.
"I don`t believe there is any case for industrial action tomorrow, not least because talks are still on-going," the leader told Parliament on Wednesday.
"It`s only a minority of unions who have taken the decision to go ahead and strike," he added.
UK Border Agency customs and immigration staff began to walk out late Wednesday as travellers coming into Britain were warned to expect lengthy delays at airports, rail stations and ports.
Four trade unions will take part in the action which one labour union warned could kickstart the most widespread industrial unrest in Britain since 1926.
Cameron insisted that the government`s planned reforms were "fair to taxpayers" and the public sector.
Under the proposals, public service workers will pay more into pension schemes and retire later as Britain grapples with a pension shortfall attributed to increased life expectancies.
The Conservative-led coalition has been the focal point of public sector anger after it announced a two-year pay freeze and 30,000 job losses by 2015 in an attempt to rein in a record budget deficit.
Around 220,000 members of the National Union of Teachers (NUT) and 55,000 from the University and College Union (UCU) will strike along with 250,000 civil servants in the Public and Commercial Services (PCS) union.
The Association of Teachers and Lecturers (ATL) will also join in the action, the first time its members have gone on strike in its 127-year history.
Unison, the largest public sector union, will not be striking after it opted to continue talks with the government.
"But if the government does not move, we will move towards strike action this autumn," a spokeswoman said.
Unison general secretary Dave Prentis earlier this month warned of waves of industrial action. "It will be the biggest since the general strike (of 1926)," he told The Guardian newspaper.
NUT leader Christine Blower echoed Prentis`s prediction.
"This is a co-ordinated campaign and we happen to be in the first phase of it, she told Thursday`s Times newspaper.
"It`s entirely likely that other unions may make decisions for the autumn."
Conservative minister Francis Maude on Wednesday claimed the action was "unnecessary and premature" and told those likely to be affected that the government had drawn up alternative plans.
"The majority of civil servants and teachers themselves did not vote for this action, showing how extremely limited support is for this strike," he said.
"We can assure the public that we have rigorous contingency plans in place to ensure that their essential services are maintained," added Maude.
PCS leader Mark Serwotka attacked Cameron`s earlier comments.
"Don`t tell low- and medium-paid workers on strike...in defence of their modest pensions that they are being unfair on the `hard-working taxpayer`, as if public sector workers are not in that category too," he wrote in the Guardian.
"We have 30,000 members not on strike today who work in the private sector," continued the union chief.”
"They do not begrudge their fellow members a penny of pension, because it is not public sector workers who exploit them but their private sector employers."
Opposition Labour leader Ed Miliband, often lambasted for his perceived closeness to the unions, criticised the strikes as "a mistake" and "a sign of failure".
A ComRes poll commissioned earlier in the week showed that just under half of the public believed that the workers had a legitimate reason to strike.
Large-scale industrial action is rare in Britain, which loses around half as many days to strikes as the EU average.