A health and safety expert has complained a digger restoring Oxford's Castle Mound was working precariously on its slopes.

Nigel Spawton, of GBS Architects in Becket Street, which provides health and safety advice to construction firms, snapped a picture of the digger working on the £150,000 project to repair landslips on the ancient monument.

He initially threatened to report the county to the Health and Safety Executive because he feared for pedestrians walking below if the digger toppled. He contacted the council contractor, Greenford.

However, the machine is now working on a broader flat platform and last night the county said a full risk assessment had been done before work started.

But Mr Spawton, 48, said: "This was potentially dangerous for members of the public and it could have proved fatal.

"If that two-tonne digger came tumbling down the mound, the fence running alongside the pavement in New Road would have had no effect whatsoever.

"The contractors should not have positioned the digger on such a steep slope and initially the work to remove the soil should have been done by hand.

"Pedestrians should not be allowed to walk past the foot of the works where the excavator could fall, or where there could be a heavy landslip caused by rain."

Mr Spawton said he was not going to report the matter to the Health and Safety Executive because he was now satisfied with the new level area for the digger since his complaint.

Greg Lowe, the council's principal repair and maintenance officer, said: "The excavator is being operated within safe working limits.

"The council's appointed health and safety planning coordinator, who it should be noted is a former health and safety executive inspector, has approved the method of repair and is monitoring work on site.

"As required by the legal construction design and management regulations, the contractor carrying out the repairs to the Castle Mound provided the council with a Health and Safety Plan and Method Statement for the project, prior to the start of repair work.

"This included arrangements for removal of the slipped soil from the Castle Mound by excavator."

In February last year, landslips on the New Road side of the monument led to safety fencing being put along the pavement.