Thousands of Sussex pupils are being taught in mobile classrooms.

Despite Government claims that school buildings are improving, there are still 208 temporary cabins in schools in East Sussex and 336 in West Sussex.

Britain's biggest teaching union, the National Union of Teachers (NUT), last night called for an end to long-term temporary classrooms and warned they were damaging pupils education and increasing the likelihood of attacks on teachers.

The figures have been released by the Department for Education and Skills from information supplied by local education authorities.

Previously, the Government has only released figures on the number of schools dependent on mobile classrooms.

These have fallen during the past year, from 170 to 159 in West Sussex and from 96 to 79 in East Sussex.

Today's disclosure means that each of those schools has an average of at least two.

A spokeswoman from the NUT said: "Temporary classrooms are not satisfactory for children's education. They create vulnerability. Teachers working alone late at night are more likely to be attacked."

She said temporary classrooms were sometimes used during construction but the union advocated them being replaced with permanent structures as soon as possible.

Lewes Liberal Democrat MP Norman Baker said: "There is a huge backlog of work, inherited from the days when the Tories did nothing about it. The Government's made some inroads but not enough.

"PFI arrangements also mean that natural extensions have become prohibitively expensive and so schools are using mobile classrooms to provide more space."

East Worthing and Shoreham MP Tim Loughton, a Conservative, said many schools were having to use temporary classrooms during rebuilding works.

But he added: "This is not a long-term solution and I hope it's not a question of children being taught in very sub-standard accommodation.

"Despite all the extra spending the Government is putting into education, it seems not enough is reaching the sharp end."

Conservative colleague Charles Hendry, MP for Wealden, said: "It makes one very suspicious when the Government says it is rebuilding every school.

"They talk a good talk but we have got to be suspicious about what they are actually delivering."

Schools minister Jacqui Smith said modern temporary classrooms often provided a pleasant working environment.

She said: "Modern, high quality mobile or demountable classrooms provide a good environment for teaching and learning where there is a short-term need. They might, for instance, be needed to cope with a short-term increase in pupil numbers.

"Or where extensive remodelling or rebuilding of permanent accommodation means providing temporary accommodation on the school site, rather than transporting children elsewhere."

Ms Smith also stressed Government funding for capital investment in schools across the country had increased from £700 million in 1996/97 to £6.3 billion in 2007/08.

She said: "Progress is being made year-by-year in improving the quality of the school building stock."

Earlier this year, the DfES disclosed Sussex schools needed repairs costing more than £140 million over the next five years.

That figure, also calculated by the LEAs, covered upgrading classrooms and other buildings to a "serviceable state", as well as providing modernisation and refurbishment. It included £28.5 million in East Sussex and £87.3 million in West Sussex.