Digging a £1.7bn tunnel near Stonehenge would cause “devastation on a major scale”, an archaeologist has warned.
Kate Fielden lives near the ancient monument and said the landscape would need to be “gouged out” to create the two-mile (3.2km) tunnel along the A303.
Transport Secretary Grant Shapps approved the project against the recommendations of planning officials.
Janice Hassett of Stonehenge Traffic Action Group welcomed the decision, saying it would reduce congestion.
The Planning Inspectorate had recommended Mr Shapps withhold consent, but the Department for Transport said that the benefits of the scheme outweighed the harm.
However, many campaigners are worried that the work will have a detrimental impact on Stonehenge, with the tunnel set to be built within a few hundred metres of the world heritage site.
Ms Fielden said: “The landscape to each side of the tunnel will be gouged out into deep cuttings with dual carriageways in them, huge tunnel entrances, masses of concrete, major road interchanges to each side of the World Heritage Site. This is devastation on a major scale.”
Tom Holland, from the Stonehenge Alliance, said he was “stunned” that the government had decided to give the plan the green light.
“I’m disappointed and I’m very surprised because the independent Planning Inspectorate recommended to the government that this scheme not go ahead.
“Basically, I’m stunned that they have decided to continue with it. This is going to cost not millions, but billions of pounds.”
Salisbury MP John Glen said the tunnel was needed, but understood the objections to the project.
“It was never going to please everyone but we have got to move forward and not have continued uncertainty on what is a significant World Heritage Site.”
The announcement has been welcomed by Stonehenge Traffic Action Group.
“I’m absolutely ecstatic,” spokeswoman Janice Hassett said. “I’ve only been campaigning seven years, but a lot of people have been waiting 30 years for this.
“We suffer greatly from this rat-run traffic and the only way to fix it is to do something about the A303. It’s well over capacity,” said Ms Hassett.
Highways England and English Heritage also support the scheme, which is expected to begin in 2023 and take five years to complete.
There is a six-week period in which the transport secretary’s decision can be challenged in the High Court.