There are fears that funding for Oswestry Innovation Park, on the edge of the town near Mile End, might lapse if the problem isn’t quickly resolved.
It was thought traffic would access the proposed business park from the Mile End roundabout, but Highways England is now looking into alternative options.
It casts major doubt over the plans for the park, which would be 60 acres in extent and attract large businesses.
According to the deputy leader of Shropshire Council, Councillor Steve Charmley, the road agency is considering introducing slip roads off the A5.
He said: “It’s all down to discussions with Highways England.
“Access which they approved at the start, they now say they don’t think is viable with how much traffic they are predicting – so we have been forced to look at different options.
“We’re looking into slip roads into and out of the site from the Wrexham and Shrewsbury directions.”
Councillor Charmley said he hoped the first ground would be broken by the end of the year but Shropshire Council is unable to apply for planning permission until there is a clear access plan in place.
Bosses behind the plans are bidding for funding from the Marches Local Enterprise Partnership (LEP) which has about £7 million available, but they need to act quickly, Councillor Charmley warned.
He added: “It’s still on track but we really do need to get the access sorted.
“It has to be sorted before we can put in for planning permission.
“It has thrown a spanner in the works but we’re hoping that we can push things forward.
“There is LEP funding available and there is still time for us to get that but if it goes on for another 12 months it will probably lapse.”
Councillor Charmley said: “However, I still do think the end of the year is a realistic target at present.”
If successful, the multi-million pound business park could create about 1,500 jobs.
Highways England asset manager, Patrick Thomas, added: “We’re working with the council as we look at developing a joint strategy to manage the impact of development at the junction.”
Last month it was revealed that an examination is to be carried out on the site as it was used as a Prisoner of War camp in the First World War, in order to determine whether any archaeological remains hold any significance ahead of any work starting.