Campaigners fighting to save a defunct Teesside blast furnace claim a task force set up by the local mayor presided over a "whitewash" after recommending it should be dismantled.
Redcar's former steelworks closed in 2015 and the blast furnace and other structures are due to be taken apart.
Save our Steel Heritage said the task force report had "no substance".
Tees Valley Mayor Ben Houchen has previously warned the cost of keeping the structures was "astronomical".
The task force, chaired by Redcar's Conservative MP Jacob Young, concluded any artefacts relating to industrial architecture should be dismantled and salvaged for memorials or displays.
Geoff Taylor, chairman of the heritage group which wants to illuminate the core of the furnace at night to showcase the area's iron and steelmaking history, said: "We feel this has been a whitewash and are extremely disappointed at both the conclusion and how the process has been handled."
He added the report prepared by the task force had "no substance, no reference to documents used in its preparation and is very lightweight".
A previous report, which formed the basis of the task force's findings, has been called "flawed" by campaigners.
Conducted by engineering consultants Primetals, it said preserving the blast furnace could cost £35m over 10 years.
Dismissing criticism of the task force findings and the earlier report, Mr Young described Primetals as "internationally respected" and said he trusted their document "completely".
Economic analysis and a survey of 200 people which saw more than half say they wanted the structure dismantled "cannot be ignored", he added.
Mayor Houchen has warned more than 800 new jobs could be blocked by a failure to develop the site on which the blast furnace stands, the Local Democracy Reporting Service said.
He said: "Communities across Redcar and the wider region want to see the former steelworks re-born and for it to be home to good quality, well-paid jobs once again."