The International Council on Monuments and Sites (Icomos) is understood to have lodged an objection to proposals for the former Aga Foundry in Coalbrookdale.
Shropshire Homes wants to build 101 homes on the site, which closed in 2017.
A planning application for the development was submitted earlier this year, with Telford & Wrekin Council expected to take a decision on the proposal.
A letter from Icomos, which provides recommendations to Unesco on World Heritage status, has been submitted to the council, but has not yet been made publicly available.
Telford & Wrekin councillor for the Ironbridge Gorge Carolyn Healy had said the letter focused on several issues, including concern "the lower reaches of Coalbrookdale will be transformed from an industrial landscape into a dense, high-rise housing estate".
She said she would be asking the application is deferred.
A spokeswoman for Telford & Wrekin Council confirmed the authority was now in discussions with Icomos over its concerns.
She said: “Planning and listed building applications for the former Aga casting works in Coalbrookdale were submitted in April 2021 for its redevelopment and the erection of 101 dwellings.
“The applications have now undergone public consultation and the local planning authority has been liaising with all statutory consultees to consider the scheme which has brought forward a number of amendments.
“Historic England – the statutory consultee for scheme – has been involved from the outset, to ensure historic assets are considered as part of this scheme.
“The International Council on Monuments and Sites (Icomos) has recently expressed an interest, raising concerns that the proposal could affect the outstanding universal value of the World Heritage site and requested to be formally consulted on the application.
“Telford & Wrekin Council is now working with Icomos and the statutory body, Historic England to document the comments and consider appropriate solutions.
“Icomos has chosen not to upload the comments to the official planning portal (which is live) and as per the normal internal process the comments will be made available in due course.”
The Shropshire Homes proposal for the site includes a block made up of 30 flats, 48 new houses, a warehouse converted into 20 maisonettes and the refitting of the Grade-II listed Power House and Pattern Shop into three more homes.
Ironbridge was designated with World Heritage status in 1986, one of the first locations in the UK to receive the designation in recognition of its contribution to the birth of the Industrial Revolution