Dumfriesshire, Clydesdale and Tweeddale MP David Mundell has called for urgent action after a section of road in Dumfries and Galloway collapsed into a stream.
The stretch of road on the A708 between Moffat and Selkirk, near to Grey Mare's Tail, is thought to have broken off after heavy rainfall.
Diversions are in place via Blyth Bridge, Peebles and Innerleithen, causing a long detour for motorists.
Mr Mundell has now written to the Scottish Transport Minister Keith Brown, urging him to provide support to Dumfries and Galloway Council.
"“Sadly this closure is something which has been going to happen for some time and I have repeatedly called for action to have this road upgraded.”
“The A708 is a direct link route between Dumfries and Galloway and the Scottish Borders and I and others have expressed concerns in the past about the condition along stretches of the scenic route.
"Sections of the road have collapsed before with barriers put in place, effectively creating single-file traffic.
“It is now clear that repairs and upgrades are beyond the resources of the local councils and that is why I have called on the Scottish government to get involved.
"This is an important A class road and one essential to tourism, transport and local people, therefore it is imperative it is fixed as soon as possible.
“Fortunately no one was injured in this incident but without investment there could be other similar incidents. It is not enough just to repair this section - there must be a longer term upgrade of this route,”