John Glen, Conservative MP for Salisbury, said any decision to make the A303 a dual carriageway must include protection for the World Heritage site.
Mr Glen said a tunnel was the only "realistic solution".
A government feasibility study is already under way to consider the various options for the road.
Speaking in a Westminster debate, Mr Glen said the road, which runs from Hampshire to Devon, had become the "devil's highway" and "one of the most notorious traffic blackspots in the country".
He joined other South West MPs calling for the government to consider the wider economic, environmental and safety benefits of improving the road.
However, he cautioned that any plans to turn part, or all, of the 92 mile (148km) road into a dual carriageway must include protection for Stonehenge.
Mr Glen said he had been told by English Heritage, the National Trust and the Council for British Archaeology that Stonehenge would be "formally placed on the at-risk register," if a dual carriageway was constructed close to the historic site without adequate protection.
Plans for a tunnel were initially shelved in 2007 when the government said the estimated cost of Â£510m was too expensive.
"A poorly designed and badly executed" dual carriageway which could "undermine a 5,000 year old world heritage site is not an improvement worth fighting for," Mr Glen said.
Transport Minister Robert Goodwill said the government hoped an announcement on the future of the A303 would be made in the autumn.

The Chinese authorities are said to be angry at the prime minister's decision to meet the Dalai Lama, Tibet's spiritual leader, last year.
Mr Cameron told MPs that UK policy had not changed and it did not support calls for independence for Tibet.
He said he was seeking a "strong and positive" relationship with China.
The prime minister met the exiled Buddhist leader -  who has called for a measure of independence for Tibet - when he visited the UK a year ago to accept an award.
At the time, No 10 defended the PM's right to meet whomever he wants and said the meeting had been arranged to engage in "dialogue and discussion and gather a wide range of viewpoints on issues of importance".
China halted ministerial meetings with UK counterparts as a result and it was reported recently that Mr Cameron had effectively been barred from visiting the country - claims No 10 has denied.
Asked in the House of Commons about the status of Sino-British relations, Mr Cameron said the two governments planned to work "very closely together" in the future.
"Let us be absolutely clear: this government has not changed the long-standing British policy towards China and China and Tibet," he added.
"We do want to have a strong and positive relationship with China, which I believe is in our mutual benefit.
"The Chinese government is aware of our policy on Tibet. We recognise Tibet as part of China. We do not support Tibetan independence and we respect China's sovereignty."
No 10 has said Mr Cameron hopes to visit China later this year but has not given any specific details.
The Chinese authorities oppose contacts between the Dalai Lama and foreign governments but he has met a host of world leaders, including President Obama, in recent years.
A Wiltshire MP has reignited calls for a tunnel to be constructed alongside the Stonehenge monument.
[NEXT_CONCEPT]
David Cameron has said the UK continues to recognise Chinese sovereignty over Tibet amid reports of a rift with Beijing over the issue.