A popular Gwynedd campsite must find alternative emergency access in the long term, the tenant of Llanbedr Airfield has said.
Shell Island, near Harlech, is cut off during high tide and the only access for emergency vehicles is through the airfield.
The owners said its future is in doubt after Snowdonia Aerospace LLP "withdrew" guaranteed 24-hour access.
But Snowdonia Aerospace said access has never been guaranteed.
A temporary arrangement is now in place, where emergency services have to call a mobile number for a staff member to open the gate and escort them over the airfield.
A Snowdonia Aerospace spokesman said: "Unfettered, uncontrolled and guaranteed third party access" would be "impossible" in an operational airfield.
He said the company told Shell Island "on several occasions" it was prepared to meet to discuss the matter, but that the campsite owners "have advised they do not consider a meeting with us conducive, while the threat of stopping emergency access remains in place".
"Our door remains open to both Shell Island and the emergency services in the immediate future, however it is clearly apparent a longer term solution is required which avoids the need to access across the airfield during high tides.
"We will be unable to guarantee future access due to operational safety, CAA regulations and ongoing development plans."
Edmund Bailey, a surveyor and agent for Shell Island, said the campsite was keen to find a solution and that its priority was the safety and well-being of staff and visitors.
"Access for the emergency services has never been in question in the past as historically the airfield had a continuous manned guard presence at the gates, sufficient to check that it was safe to pass through without delay.
"Shell Island has never completely refused to meet Snowdonia Aerospace," he added. "A meeting provisionally scheduled for 10 April was cancelled by Snowdonia Aerospace and no further date has been offered.
"We wanted to sort this out privately, it went public because the emergency services required that the site needed to notify visitors of the proposed changes to access arrangements and this only happened after we notified the owners of the airfield in advance."