An MP has demanded subsidence on the A14 be 'sorted fast' as new information reveals temporary repairs are failing.

A 50mph speed limit has been reintroduced at the Rougham crossroads to ensure drivers' safety but, despite months of investigation, the Highways Agency is still unsure what has caused the subsidence.

Ranjit Mistry, route performance manager for the Highways Agency, told David Ruffley, MP for Bury St Edmunds and Stowmarket, initial investigations highlighted two possible causes but further surveys were still needed before permanent repairs could take place.

In a letter, Mr Mistry said: "The temporary repair to the area of subsidence is now starting to fail. I would, at this point, like to reassure you that the A14 is not unsafe.

"However, to ensure the safety of all road users, particularly powered two-wheeled vehicles, we have reinstated the advisory 50mph signs on the approach to the area and our incident support units will monitor the condition of the temporary repair daily."

Investigations, which are set to take place on Wednesday, include CCTV surveys of drainage, tests on ground moisture levels, depth and the extent of defective sub-layer material, as well as water testing of the drainage system.

Mr Ruffley said: "After millions of pounds of taxpayers' money has been spent on Rougham crossroads, the Highways Agency still can't give us a straight answer on the subsidence problem.

"This is a matter of public safety and it needs to be sorted fast."