The whole of the Cotswolds is “too large” to be made one national park, an MP who has championed the move has said.
Last month, the Glover report described the Cotswolds and combined Dorset and East Devon Areas of Outstanding Natural Beauty (AONB) as “leading candidates” to adopt the status.
MP David Drew said the whole Cotswolds AONB cannot sustain park status and wants the boundaries defining.
Defra is considering the report.
Environment secretary Theresa Villiers previously said: “I welcome and agree with the spirit of ambition which is in line with our 25-year environment plan, and we will now carefully consider the recommendations set out in the review.”
Defra has not yet responded to a BBC request for comment regarding Mr Drew’s call for defined boundaries.
The Cotswolds, which is made up of the Cotswold Hills, covers 790 sq miles (2,045 sq km) across Gloucestershire, Oxfordshire, Wiltshire, Somerset, Worcestershire and Warwickshire.
Labour MP for Stroud Mr Drew, who put the case forward for national park status in the Cotswolds, said: “The boundaries of the AONBs are probably so widespread that you are taking in a huge area.
“We would be by far the biggest national park so I do think we need to look sensibly about what should be in it and what shouldn’t be in it, but again that should be open to discussion.
“The main thing is the Cotswolds should be accessible to people from all manner of large urban spaces, Birmingham, Bristol, Bath, and so on.”
He added that he had no preconceptions over which areas should or should not be included as this was for public debate.
The Cotswolds’ current AONB status means it gets less funding and planning powers than it would if it was named a national park.
The report has also said the Forest of Dean should be upgraded to a National Landscape – the new name for AONB.