Bringing all schools up to scratch will cost �785m, the study found

Research by the Welsh edition of the Times Educational Supplement says there is a backlog of repairs in more than half of all Welsh local authorities.

It claims buildings at one in five secondary schools are below standard.

The assembly government said almost �630m had been spent on repairs and the shortfall should be cleared by 2010.

The Times Educational Supplement (TES Cymru) survey found the repairs needed in 14 of Wales' 22 local authorities totalled �500m.

The other eight authorities did not contribute to the research but, by averaging out the figures, TES Cymru has estimated the total bill for Wales is �785m.

REPAIRS BACKLOG Carmarthenshire: �20m Gwynedd: �25m Newport: �25m Pembrokeshire: �25m Denbighshire: �37m Rhondda Cynon Taf: �55m Powys: �60m Cardiff: �67m Vale of Glamorgan: �87m Wrexham: �90m Monmouthshire: �130m

The cost of building repairs to make schools "fit for purpose" ranged from �25m in Pembrokeshire to �130m for Monmouthshire.

The bill included adaptations and additions that local education authorities would need to make to their schools to comply with disability access laws.

The study comes after the 2005 report by the Welsh schools inspection service, Estyn, found the condition of secondary schools is 'good' or 'very good' in only a quarter of cases.

A Welsh Assembly Government spokesperson said: "We were committed to invest �560m over the lifetime of this assembly to improve school buildings.

"This commitment has been more than met with investment already standing at �629m.

"All authorities in Wales receive significant assembly support for improvements to buildings and associated facilities in schools.

"This level of investment is beginning to have an impact on the state of schools buildings, though there is still significant work to be done.

"Over the autumn we will be reviewing the position with each authority against the 2010 target."