Botched workmanship led to this week’s partial closure of the Queensferry Crossing, a senior Scottish Government official has admitted.
The Fife to Edinburgh link will shut to southbound traffic for five days to carry out snagging works.
Michelle Rennie, director of major transport infrastructure projects at the Scottish Government, said the delay is down to a “workmanship issue” with road surfacing around the bridge’s joints.
She added there is likely to be some further lane restrictions until September, when the contractor is still liable for all snagging works.
“It’s a workmanship issue, the design is correct, but the surfacing wasn’t laid to the tolerances set out in the design,” Ms Rennie told MSPs on the reason for this week’s planned closure.
Ms Rennie said the issue was first known about in August, before the bridge was opened to huge fanfare, but the response was not decided.
Tory MSP Jamie Greene asked why the public was only told about the partial closure on Monday when the government knew about the surfacing issues before the bridge was opened in August.
Ms Rennie said: “The contractor hadn’t designed the solution to this until probably a couple of weeks ago and like I say the thing that causes the greatest disruption on the road network is driver confusion, so what we didn’t want to do is put out dates and change those dates.”
Speaking after the meeting, Mr Greene said: “At no point were road users, whose daily lives are now thrown into disarray, informed that there were impending closures.
“To make matters worse, we now know that there are potentially more closures to come.”
Alex Cole-Hamilton, the Lib Dem MSP, said: “During the lavish fanfare of the opening back in September the Scottish Government made no reference to the fact this would have to be fixed.
“Cutting the ribbon on the bridge was rushed to avoid financial penalties or adding to the existing eight month delay.
“It is an insult to the public that ministers didn’t tell them closures were on the way.
“We need to know exactly what other works are in the pipeline to make the bridge fully operational and how this will impact upon its users.”
Southbound traffic will be diverted along the Forth Road Bridge during the works. They are due to start at 10pm on Thursday and finish at 6am the following Wednesday.
The speed limit will be 40mph on both bridges during this time.
It is estimated the delay will be “two to four minutes at morning and evening peaks”.
Asked whether there would be further closures, Ms Rennie said: “There will be some lane restrictions happening between now and September, yes.”
She told the rural economy and connectivity committee that they have always made clear there will be “finishing and snagging works required”, which could include fixing mechanical and electrical issues.
On why they were not carried out before the opening, she said: “There was no need to delay opening the bridge for that sort of thing. These are relatively normal.”
This week’s works will pave the way for the speed limit to rise to 70mph, Transport Scotland has said.
The £1.35bn structure, which is the UK’s tallest bridge, was officially opened in early September after a series of delays.