Ferry ports and cross-Channel rail services linking Britain to continental Europe, also operated largely as normal.
The strike is the biggest test so far of Prime Minister David Cameron's Conservative-Liberal Democrat government, which sparked the unions' fury by making public sector workers pay more into their pensions and work longer.
Anger rose further on Tuesday when finance minister George Osborne targeted the pay of teachers, nurses and soldiers and revealed plans to cut an extra 300,000 public sector jobs as he sharply reduced Britain's growth forecasts.
Osborne infuriated the unions by announcing a new two-year, one per cent cap on public sector pay rises.
Cameron was scathing about the strike, telling parliament it had been a ``damp squib'' and lambasting unions for calling the action while negotiations on pensions were ongoing.
The prime minister insisted that reforms to public sector pensions were "absolutely essential'', and accused Ed Miliband, leader of the opposition Labour Party, of being "irresponsible, left-wing and weak'' for refusing to condemn the strike.
The Unison union said two million workers had taken part in the stoppages, and claimed they had wider support.
Brendan Barber, general secretary of the Trades Union Congress (TUC), said the government had put the public sector ``under attack'' and the strike was fully justified.
"There comes a time when people really have to stand up and make a stand,'' he told ITV television.
"With the scale of change the government are trying to force through, making people work much, much longer and get much, much less, that's the call people have made.''
In Salford, northwest England, around 30 garbage collectors manning a picket line outside their depot dismissed claims that their pensions were ``gold-plated'' compared to those in the private sector.
Neil Clarke, a union organiser with Unite, said: "The government is attacking our pension schemes - they are looking for public sector workers to contribute more, work longer and receive less in pension benefits.
"The average public sector pension comes in at STG3000 ($A4700) a year. Could you live on STG3000 a year?''
A giant union rally took place in Birmingham, Britain's second city, and unions said 300,000 workers downed tools in Scotland.
British diplomats abroad were also involved in the strike, with the United Nations, Washington, Paris and all major capitals affected.
Under the government's proposals - which form part of its efforts to slash the budget deficit - public sector workers will have to work until they are 66 and increase the amount they pay into their pensions.
But staff face a lower pension payout, which will be based on their average salary as opposed to the final salary schemes to which they are currently tied.
- AAP
