A strike by up to two million public sector workers over pensions will cause widespread disruption on Wednesday, hitting schools, hospitals, airports, courts and libraries.

The Government believes two thirds of schools will close because teachers, headteachers and classroom assistants from all the education unions will be on strike.

Parents will have to make alternative childcare arrangements, work from home, or take their children to work where practical. Chief secretary to the Treasury Danny Alexander said he might take his daughter to his office because her school is closed.

Passengers at airports and ports have been warned to expect huge queues because of action by immigration and passport officers. The Border Agency has been seeking volunteers from other parts of the civil service to cover for the strikers.

Delays at Heathrow could last as long as 12 hours and airlines were warned of "mass cancellations" of departing aircraft. Northern Ireland's public transport system will be shut down, and the Tyne and Wear Metro will be hit, but transport in other parts of the country will not be affected.

Meanwhile, thousands of NHS operations and appointments are being cancelled and rescheduled because of action by NHS staff ranging from nurses to radiographers.

Services including refuse collection and street cleaning will also be hit, libraries, leisure centres and swimming pools will close, and in some areas parking tickets will not be issued because traffic wardens will be on strike.

Jobcentres will close, Government departments will operate on skeleton staff - and MPs might have problems buying food in the Commons because catering workers are among those taking action. Thousands of courts staff will also join the day of action, causing the cancellation of cases and closure of many court buildings.

Mr Alexander told BBC Breakfast he had seen no sign that trade unions were going to decide not to go on strike on Wednesday: "It is a badly timed strike that is occurring right in the middle of these discussions, and a big distraction from those discussions.

"The fact remains that people in the public sector will continue to get among the very best pension schemes available to anybody. People will be asked to work longer and to pay in a bit more, but, actually, for most people, particularly on low and middle incomes, particularly for female workers, they would get a better pension at retirement than that which they can expect now."