Liverpool could be stripped of its World Heritage status as early as next year.
The latest warning to the city came as UNESCO told the Government to clamp down on civic planning decisions that affect its iconic waterfront.
Dresden remains the only location that has seen its World Heritage status revoked but Liverpool now faces the threat of joining the Germany city.
Papers written for next month’s World Heritage Committee meeting warns of “highly adverse and irreversible impacts” of planned building developments.
Save Britain’s Heritage identified Liverpool Waters as a key concern with the scheme set to transform the face of the waterfront with several skyscrapers.
Liverpool has been on the World Heritage status’ ‘in danger’ list since 2012 due to concerns about the £5.5 billion redevelopment plans by Peel.
Henrietta Billings, director of Save Britain’s Heritage, said: “This is a final warning shot for Liverpool and the British Government.
“International heritage status doesn’t just put Liverpool on the world stage, it brings cultural tourism, urban regeneration, and sustainable visitor attractions.
“Losing it because of crass planning decisions would be an international embarrassment as well as a hugely costly mistake.”
Save Britain’s Heritage claim that the papers from severely condemn the UK’s Department of Culture, Media and Sport for Liverpool’s poor maintenance.
Kosovo and Georgia also face the threat of being stripped of World Heritage status but tourism chiefs in the city have called for the Government to act.
Jonathan Brown, director of Liverpool-based planning and tourism consultancy Share the City, said: “Karen Bradley (the Culture Secretary) needs to get a grip on her advisors before this little local difficultly becomes an international incident.
“The UK usually honours her international treaty obligations, but UNESCO have clearly run out of patience with government assurances backed only by inaction.
“The United Nations expects the world’s cultural treasures to be safe in our hands, and a breach of the treaty would be noted with sadness around the world.”
However Liverpool City Council insist that its UNESCO status, which it has held since 2004, has been maintained despite the city’s continually changing face.
A spokesman said: “Liverpool has made great strides to protect its World Heritage Site and in many ways the city has set a new bar in conservation efforts and was recently given European “Heritage Role Model” status.
“Historic assets within the site have received almost £750m of investment including the upgrade of 37 listed buildings over the past 10 years.
“The city has also created a new management plan, which has been endorsed by Historic England and we’ll be sharing that with UNESCO in July.
“However, Liverpool is also a city undergoing a £13bn renaissance and the right balance needs to be found where regeneration and conservation can complement each other as is the challenge in other cities like Edinburgh and Westminster.”