Costain/Skanska is working on the project under a £314m ECI contract to tackle a 34km section of the road running roughly from Huntingdon to Cambridge.
On the design side, Atkins and WSP have also been involved.
Chief Secretary to the Treasury Danny Alexander yesterday said the project would be delayed as part of a wider series of project cuts to save £2bn, but gave no indication of when the important upgrade job could be resurrected.
The uncertainty means the large project team is certain to be disbanded, although the firms say it is too early to comment.
The project team has worked on the Fen Drayton to Histon section of the scheme since January 2008.
Since that time some 640 people have worked on the project and nearly 8,000 drawings have been produced in anticipation of work starting in spring 2012.
One of the contractors said: “This is all very dissapointing and we will have to explore what this announcement means in detail.”
A spokesman for Atkins said: “We are working to understand what the government’s announcement means to us with our client.”