ArcelorMittal has told Michael Gove it may be forced to "cease operations in Britain" unless he blocks the redevelopment of Chatham Docks in a letter obtained by Sky News.
The world's second-largest steel company has warned the government that a planning verdict due this week could lead to a key division quitting the UK.
Sky News has seen a letter sent by ArcelorMittal to Michael Gove, the levelling-up secretary, in which it says that a decision to allow the closure and redevelopment of part of Chatham Docks would have "seismic adverse consequences… [for] the British economy and multiple strategic industries".
In the letter from Matthew Brooks, who runs ArcelorMittal's construction solutions arm in the UK, the company urges Mr Gove to issue an urgent order to allow fuller government scrutiny of the redevelopment proposals ahead of Wednesday's decision by Medway Council.
"This is highly time-sensitive - calling in the application after next Wednesday will not be possible," Mr Brooks wrote.
He warned that if the proposals were approved, ArcelorMittal would "regrettably be left with no alternative but to leave Chatham Docks and, more than likely, cease operations in Britain, given the lack of suitable alternative sites".
"This, too, would likely be the case for the majority of businesses at the Docks," Mr Brooks wrote.
"This would have a significant impact on Britain's manufacturing and construction industries, delay countless critical national infrastructure projects, come at a significant cost to the economy, and leave Britain vulnerable and exposed to the volatility of international supply chain shocks."