Lane restrictions on the Queensferry Crossing, such as the closure of the southbound carriageway from tonight, will continue over the next 10 months due to “snagging” issues, MSPs were told.

Transport Scotland announced on Monday the new £1.35 billion bridge would close to southbound traffic from 22:00 hours for five days of surfacing works to be carried out.

The works will allow the bridge to achieve its next key milestone – opening at a 70 mph speed limit – as planned by the end of December subject to weather conditions, it said at the time.

But the body’s director responsible for the structure, Michelle Rennie, has said further restrictions will be enforced at times up until September.

She also said the problem had been known about before the bridge opened in August but a solution was only devised two weeks ago.

Speaking to the Scottish Parliament’s rural economy and connectivity committee, she said: “We have been consistently saying that there will be finishing and snagging works required. The contract allows for those works to happen up until next September, at no additional cost.

“There will be some lane restrictions happening between now and then.”

Ms Rennie said the fault was only announced on Monday once a clear weather window had been established for the repairs to go ahead. Southbound traffic will be switched to the Forth Road Bridge from 10pm tomorrow until 6am next Wednesday. Northbound traffic will continue to use the Queensferry Crossing, with the speed limit reduced to 40mph.

The warning came as MSPs were told the fault was caused by a workmanship error.

Ms Rennie told the committee: “The snagging issue is not due to the joints, but the level of surfacing around the joints. It was laid marginally too high.

“That’s a workmanship issue. It’s the road surfacing at fault. The surfaces were not laid to the tolerances set out in the design.

“There is concern about the impact of use of the road at 70mph on the joints.”

Ms Rennie said officials had not wanted to alert the public to the problem until firm dates could be fixed for the repairs.

The cost of the repairs will be paid for by the Forth Crossing Bridge Constructors (FCBC) consortium which built the bridge.

Ms Rennie also admitted some of the bridge’s windshielding required further work, but “nothing in comparison with what’s been reported” and that it was expected to be done at the same time as the surfacing work.