Plans for a dual carriageway on a busy commuter route into Cambridge have been shelved for at least two years.
A scheme to widen the A428 has already gone through a public inquiry but now the government has pulled the plug.
With plans for a five-mile dualled road on hold, a spokesman said regional transport authorities would now decide if it was still a priority.
Work had been scheduled to begin in March 2006 but is delayed until 2008 at the earliest.
It was meant to coincide with work to improve the A14 trunk road and local people are concerned about the future of roads which are becoming more congested.
Andrew Lansley MP said: "If this road has not been dualled by the time the A14 work starts and a lot of traffic ends up being diverted because of roadworks on the A14, the whole of south Cambridgeshire will be turned into a nightmare."