Schools and libraries across twenty London boroughs could restrict their services as strike action begins today.

Members of Unison, the public service union, begun industrial action today, in protest over the level of London weighting paid by their council employers.

Unison has been in dispute with the Association of London Government over London weighting since last May.

The union wants the weighting set at £4,000 for its members in the capital, but the ALG says it can only afford to pay a maximum weighting of £2,600.

The strike by staff at schools and libraries will last until Friday, and will be followed by another three day strike between May 20 and 22.

The ALG says about 20 schools will be affected by the strike.

Unison says many of its members working at schools and libraries in London have to take second jobs to provide for themselves. Unison's change in tactics, targeting schools, is a deliberate move to persuade the employers to make a better offer, with the aim to "target those services which have a direct impact on the public".

A spokeswoman for Enfield Council said efforts would be made to minimise the effect of the industrial action.

She added: "To limit any harm that may come to children's education, especially as some are sitting their SATs, we have asked schools to priorities education needs so the schools will not close totally."