URGENT repairs to the Forth Road Bridge have been planned for later this year after engineers concluded that nearly 1000 heavy duty bolt assemblages would need to be replaced, at a cost of £5 million.

Engineers embarked on emergency repairs earlier this year after 17 cracked nuts were discovered on the bands that secure the vertical steel ropes to the two main suspension cables, causing significant delays to motorists.

But they have now concluded that all 944 bolt assemblages will have to be replaced to avoid further corrosion and the consequent disruption caused by emergency repair work.

The Forth Estuary Transport Authority (Feta), which operates the crossing, said yesterday it was planning to sidestep European procurement rules in order to start work before winter, when such work would be especially disruptive.

Barry Colford, chief engineer and bridgemaster, stressed that the bridge was not unsafe but said motorists could face more delays later this year if further cracks appeared.

"Until we have replaced all of these bolt assemblies, it is quite possible that further emergency repairs will have to be carried out at short notice," he said.

"So far we have been able to limit the disruption, but this would become increasingly difficult if failures occur during the winter when light and fair weather are in shorter supply."

Feta, which has seen its capital funding cut by 56% over three years, is expected to raise £850,000 of the funds, with the remaining £4.15m provided by the Scottish Government. It admitted this may cause other work to be deferred.

Problems with the cable band bolt assemblies were first discovered in 2007 and a long-term programme to replace all the nuts was put in place, which was due to cost £530,000. However, engineers have now concluded that they will have to be redesigned.