Teachers, hospital staff and border guards walked out on Wednesday as up to two million state workers staged Britain's first mass strike for more than 30 years, adding to pressure on a government facing an economy flirting with recession.

Public sector employees are protesting over reforms that unions say will force them to work for longer before they can retire, and pay more for pensions which will be worth less.

Their anger has been fuelled by new curbs on their pay and additional job cuts outlined on Tuesday when the Conservative-led coalition government cut economic growth forecasts and said its tough austerity programme would last until 2017.

Chancellor George Osborne condemned the strike that is expected to close most schools in England and Wales, delay surgery in hospitals and could lead to long delays at ports and airports.

The strike is not going to achieve anything. It's not going to change anything, Osborne told BBC TV. It is only going to make our economy weaker and potentially cost jobs.

The government says reform is needed as people are living longer and public service pensions are unaffordable.

The strikes mirror protests in continental European countries where governments are trying to juggle budget deficits with the needs of an ageing population.

HEATHROW DELAYS AVOIDED

Airlines said on Monday they were cutting flights into Heathrow, Europe's busiest airport, because of fears of long delays and overcrowding due to the passport control strike.

The government has flown some embassy staff home and recruited volunteers from other departments to help take the place of striking border guards and delays that had been feared had not materialised on Wednesday morning.

Due to the effective contingency plans we have put in place with the airlines and the UK Border Agency over recent days, immigration queues are currently at normal levels, airport operator BAA said.

However there still remains a possibility of delays for arriving passengers later in the day.

At Heathrow, a marquee, rows of chairs and toilets had been set up outside in preparation for overcrowding.

Brendan Barber, general secretary of the Trades Union Congress, an umbrella group coordinating the strike, said workers were no longer being asked to make a temporary sacrifice, but accept a permanent deep cut in living standards when you include pay and pension contributions.

Our economy can afford decent pensions, the cost of public sector pensions is due to fall over coming decades, Barber told Sky News. We're not going to solve our problems in our economy by hammering down the living standards of six million public service workers.

A coalition of 30 trade unions are taking part in the strike, billed as the biggest walkout since action during the Winter of Discontent in 1979 that helped Conservative leader Margaret Thatcher sweep to power.

Unions say ministers are unwilling to negotiate, and Dave Prentis, who heads Unison, a union representing 1.4 million workers, said his members were angry that the changes were designed to cut the deficit not go towards pensions.

How can you be expecting low-paid women to be hit so badly with their jobs, privatisation, and now their pensions when the top 1 percent in our society have increased their wealth by 30 percent in the last year, he told BBC radio.

He has warned more strikes could follow next year if the government failed to budge.

(Additional reporting by Michael Holden and Keith Weir; editing by Diana Abdallah)