The A59 will remain closed until March after heavy rainfall has forced contractors to carry out further work on the crumbling hillside at Kex Gill.
The major route was due to re-open at the end of this month, however extra drainage and stabilisation works has pushed back the date by around 10 days, meaning it is now not expected to open again until the week beginning March 7.
The news is likely to be a blow to drivers who regularly use the road, which runs across high ground between Skipton and Harrogate, as well as fed-up residents and businesses who have been impacted by the closure.
North Yorkshire County Council's executive member for Highways, Coun Don Mackenzie, said: "Stabilising these steep slopes above the A59 is a difficult and complex operation which is entirely weather-dependant.
“We are fully aware of the urgency of the work and our contractor is working seven days a week during daylight hours to progress the work as quickly as possible.
"The slopes are steep and this high ground subject to harsh weather conditions. Unfortunately, after last weekend’s heavy rains, our monitoring of the slope has revealed the need for additional stabilisation and drainage works to move water away from the slope.
“We appreciate the inconvenience that this closure is causing, but safety of the travelling public remains paramount and I can reassure motorists that we will reopen the road as soon as it is safe to do so.“
The county council was forced to shut the A59 on January 5 after substantial cracks were detected on the hillside as a result of heavy rain over the Christmas period.
Parts of the slope had shifted by up to 800mm and there was concern about the amount of water that had become trapped and pooled at the top of the area of instability.
The county council's contractors began work on January 18 to install a solution designed by geotechnical engineers to drain the water from this area using a drainage channel.
These works, which are weather dependent, were expected to take up to six weeks.
However, as a result of further heavy rainfall last week, the authority says contractors must now provide additional drainage measures and strengthen the retaining wall at the bottom of the slope adjacent to the A59.
Some of this work can be carried out at the same time as the current drainage work. But there is a section on the slope below the drainage works, which the contractor will need to work on separately for safety reasons.
The combination of the recent poor weather and the extra drainage works will therefore extend the construction time, pushing back the re-opening of the road.
Last week the Harrogate Advertiser revealed plans to build a bypass that would re-route the A59 away from Kex Gill have moved a step closer after senior councillors approved a new transport plan for North Yorkshire.
The cost of the scheme, which is aimed at improving east-west connectivity, is currently estimated at approximately £33m.