Bridge operator Amey said the date of January 4 was dependent on the weather, but said the work was on track. Seven days were needed for the assessment and design of the repair to the bridge before three weeks of engineering work.

The bridge was closed to all traffic on after a crack was discovered in a truss under the carriageway.

Plans to fix the problem, which involves a plate welded repair to the damaged truss end link and jacking the link into position, were checked and verified by two independent specialist engineering firms last week.

An access platform was constructed to allow teams of welders to work day and night when weather conditions permit as work on the exposed area cannot be carried out when wind speeds exceed 35mph.

Amey is taking preventative action on another seven similar locations on the bridge to prevent issues from arising there, and installing structural monitoring systems. It is estimated the work will cost around £2m to complete.

Other maintenance is also being carried out while the bridge is closed, including line painting and decking work, which authorities said would reduce the need for future closures and restrictions.

A Holyrood committee will deliberate the scope of a potential “focused” inquiry into the closure of the bridge on Wednesday.