Sepa has lodged a formal objection to plans for new luxury homes on the Taymouth Castle Estate.
The environment protection agency says the location, beside the River Tay, would put people and property at risk from flooding.
And it is urging Perth and Kinross Council to reject the proposals.
Drawings on the council’s planning portal show proposed properties hard up against a new flood defence bund.
Sepa has intervened this week, saying it cannot support designs that show the ground floor below the flood level.
It wants the council to reject plans for nine homes to the east of the castle, and six to the north-east.
In letters to the council, dated September 9, it states: “The cornerstone of sustainable flood risk management is the avoidance of flood risk as a first principle.”
It goes on: “We object in principle to the application and recommend that planning permission is refused.
“This is because the proposed development may put people or property at risk of flooding, which is contrary to national planning policy.”
Sepa is also asking for changes to a third housing zone.
It wants two of the five properties at this site, to the west of the castle, removed from the application altogether.
Without these changes, it says it will also object in principle to this zone.
Sepa objection follows revised Taymouth Castle housing plans
Taymouth owner, Discovery Land Company, already has permission to build 26 homes on either side of the castle.
In time it wants to build almost 150 members-only properties on its land near Kenmore, with prices starting at £4 million.
However, it has submitted fresh plans to the council amid fears of flooding.
The US real estate firm is now seeking to reduce the number of homes around the castle to 20.
It also wants to move some of them further from the River Tay and onto the landward side of its new flood defences.
A supporting statement accompanying the latest planning applications says: “The approved location for a number of the approved dwellings lies on the riverside of the flood defence, which would increase flood risk to the properties should they be built.
“As such, the revised proposals place the dwellings on the castle side of the bund to ensure resilience to flood risk and climate change, whilst also creating a unique landscape feature.”
Perth and Kinross Council will consider the planning applications at a later date.
Homes plan latest phase of Taymouth transformation
Discovery Land Company, fronted by US tycoon Mike Meldman, bought the Taymouth Castle estate in 2019.
The firm specialises in members-only “worlds”, featuring luxury residential homes in private club communities.
Taymouth Castle is its first UK location.
The owners have so far spent more than £100 million transforming the landmark into a private members’ clubhouse.
The company has also acquired a number of properties in nearby Kenmore, including the village shop and Kenmore Hotel.
An online petition against the development, launched last year by protest group, Protect Loch Tay, has amassed more than 160,000 signatures.
But many locals welcome the project, and the jobs and opportunities it could bring.
An economic impact study, commissioned by Discovery Land Company, forecast the estate could boost the Perth and Kinross economy by £390 million over its first 25 years.
It is due for completion by the end of 2029 and is expected to provide around 250 full-time jobs.
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