London allowances from April

Inner: �3,105 Outer: �2,043 Fringe: �792

The issue is London weighting allowances, which are going up by 3.5% in April in line with the general teachers' pay rise.

The National Union of Teachers says this is not enough and is to ballot members on a strike "of up to one day" to take place before Easter.

When the annual pay rise for teachers was announced last month, NUT members in London said the 3.5% rise in their allowances would do nothing to ease the shortage of teachers.

Basic pay from April

Just qualified: �17,628 After seven years: �25,746 Upper scale: �27,894

They argue that a supplement of at least �4,000 is needed in inner London, an increase of about a third.

They want the outer London and London fringe allowances to go up by a similar proprtion.

Now the union's national executive authorised a full legal ballot of members throughout Greater London and the fringe areas.

Area by area

The ballot will be counted against individual employers - that is, each education authority and each school in the case of foundation schools.

The union's action is in support of better staffing for London schools and better education for London's children

NUT leader, Doug McAvoy

A simple majority in each count would be needed to enable a strike to go ahead in that area or school.

A spokesperson said the timing of the ballot had yet to be finalised but any action would be before the Easter break.

The union's general secretary, Doug McAvoy, said: "The 3.5% increase in the allowances does nothing to address the problems of recruitment and retention of teachers in London schools.

Quality of education

"There is continually rising turnover of staff and in the use of supply teachers to fill the gaps.

"Pupils face constant change of teachers which adversely affects their education.

"The NUT is anxious that the education secretary be in no doubt of the anger of teachers in London.

"The union's action is in support of better staffing for London schools and better education for London's children."

The last time there was action over the issue was in 1972, when Margaret Thatcher was the education secretary.

Teachers then stopped work for half a day.