Plymouth MP Linda Gilroy is warning a £470m tunnel under Stonehenge could scupper plans to improve transport links to the South West.
Planned changes to roads at Stonehenge would cost £470m
She says if the region is left to pay for the upgrades to the A303 it could leave too little leftover to pay for other transport projects.
Ms Gilroy has called a debate in parliament to discuss the issue.
Government decisions about spending on roads, rail and airlinks for the next 10 years are due to made in the spring.
Ms Gilroy said: "This is my chance to say to ministers that our roads tend not to be that reliable.
"I was disappointed we did not get the go-ahead for the dualling of the A303 to Exeter and there are other issues such as the three-hour train journey to Paddington from Plymouth which could be threatened by the rail projects in London."
Ministers said in July they would consider all options to ease traffic blight around Stonehenge after it was revealed that the costs of the tunnel had more than doubled to £470m.
The section of the A303 running past Stonehenge is one of the few remaining single carriageway sections of the popular holiday route to Devon and Cornwall.