Fenland MP Steve Barclay has hit out over warnings improvements to the A47 could take up to eight years.
Last week, a leading Highways England official said building work on six stretches of the route, which will share £300million of Government funding, may not start until 2020.
The official also warned that construction could take up to three years to complete, meaning the work could continue until 2023.
The A47 junction with the A141 at Guyhirn were among the improvements listed in the scheme, which was announced by Prime Minister David Cameron last autumn.
Mr Barclay said: “The suggestion that it should take longer than the time spent fighting the Second World War to do straightforward road works is simply not good enough and I’m working closely with neighbouring MPs to ensure pressure is being brought for greater urgency.
“The A47 needs to be upgraded and we need to start work on that as soon as possible. “
Around 20,000 vehicles use the A47 trunk road between Guyhirn and Wisbech every day and congestion, particularly at peak times, acts as a barrier to development and jobs.
Estimates suggest that around £16 million needs to be invested to create a new larger junction.