They have voted for a one day strike action over the London weighting on their salaries which they say is not enough to allow them to buy a home or raise a family.

Teachers say staff shortages in the capital will only be solved by increasing the London allowance.

The gap between cost of living and salaries is creating a two-fold problem for Tim Benson, the head of Nelson Primary School in east London.

A teacher came to me yesterday and said he was moving to Yorkshire because he could not afford to buy a house

Tom Benson Head teacher

He told the BBC's Today programme that he struggles to find full-time teachers and once he has them, they are difficult to hold on to.

"A teacher came to me yesterday and said: 'I'm going to move back to Yorkshire. I can't afford to buy a house.'

"He's 35 and he can't afford to buy a house."

Mr Benson says a quarter of his 32-strong staff have to be supplied by an agency because of a teacher shortage.

This situation exacerbates the funding problems, he says.

"A huge amount of public money is being spent on agency supply fees," he explains.

Draining resources

"A normal teacher at my school on average costs �29,000. An agency teacher is �37,000 - that's �8,000 more a year.

Shani Green: Teachers feel undervalued

"Times that by eight and I should have �64,000 to spare."

Mr Benson agreed that the government was putting more money into schools but he said that it was being wasted on things like supply teachers.

"My seven-year-olds who are doing their SATs at the moment can tell the secretary of state you can only spend that money once."

He added that the dispute over London weighting was not at the heart of the problems in London schools but it was "one of the issues".

He pointed out the difference between the allowances given to police officers working in the capital, �6,000, and teachers, �3,000.

"Hendon Police Training College is full now because of that," he added.

Teacher Shani Green, of the Cathedral School, in south east London, told the BBC that her fellow teachers believed that their London living allowance was lagging behind other public sector workers.

She said: "We feel that as teachers we are undervalued.

"Not enough teachers are working in London. There is a big shortage.

"We can't recruit and we think the London allowance would allow us to do so if there was a sufficient increase."