The head of the National Trust in Britain has appealed directly to Gordon Brown's government over fears about commercial development close to the Giant's Causeway, it can be revealed.
The charity's director general urged a Whitehall Minister to intervene in the row over a proposed private sector visitor centre at Northern Ireland's top attraction.
Details of the plea have emerged amid speculation about the Trust's next move in the centre dispute.
It is understood to be continuing to work with Moyle Council in support of an alternative to the private sector scheme tabled by property tycoon Seymour Sweeney.
Options believed to be under current consideration include the National Trust leasing the council's current Causeway centre site and car-park.
Proposals for a new visitor centre within this land are expected to be discussed at a meeting next week between National Trust representatives and Enterprise Minister Nigel Dodds.
The Trust owns the Causeway stones and claims that their status as Northern Ireland's only UNESCO world heritage site could be put at risk by commercial development.
Its director general Fiona Reynolds has relayed these concerns in a letter to the London-based Department for Culture, Media and Sport (DCMS), which has UK-wide responsibility for world heritage sites.
The letter - to Whitehall Culture Minister Margaret Hodge - has been released to this newspaper by DCMS under freedom of information.
It was sent in September and highlighted the announcement made earlier that month by Northern Ireland Environment Minister Arlene Foster.
Mrs Foster stated that she was "of a mind" to grant Mr Sweeney's Causeway visitor centre project planning permission.
Stormont's Department of Enterprise responded by shelving plans for a new publicly-owned centre, involving Moyle Council and the National Trust.
Ms Reynolds' September letter to the London Minister referred to the ground rules established by international heritage body UNESCO for the Causeway.
The Trust director general said that progress in meeting these requirements was in danger of being undermined and also expressed concern at proposals from another developer for a hotel and golf resort in the area.
Asking Ms Hodge to make contact with both the Northern Ireland Environment Minister and UNESCO, Ms Reynolds stated:
"I recognise that you will be sensitive to the responsibilities of the newly reconstituted Northern Ireland Assembly, but responsibility for protecting the integrity of world heritage sites lies firmly with the UK Government and the situation needs your intervention."
DCMS confirmed to this newspaper last month that it was compiling a report on the Giant's Causeway visitor centre controversy for UNESCO.
The London department has declined to release any recent correspondence with either UNESCO or the Stormont executive on the Causeway issue.
It cited exemptions under the Freedom of Information Act relating to both international relations and relations within the UK.
The National Trust has meanwhile highlighted its concerns about the Causeway in a "stop press" addition to a circular sent to members across the UK within the past week.