Struggling miner BHP Billiton's chief executive, Andrew MacKenzie, will warn Britain risks plunging into a lost decade if it votes to leave the EU.
MacKenzie, who has stints at commodities giants BP and Rio Tinto under his belt, will say a Brexit could spark 10 years of complex negotiations, ending in a deal which would actually leave Britain worse off.
"On trade, the EU has negotiated broadly effective deals for Europe and the UK. Restoring these agreements after Brexit would take years, perhaps a decade, of negotiation," he's due to tell an audience at the Centre for European Reform today.
The debate over the economic implications of Britain leaving the EU ramped up today, after the Treasury published its widely-anticipated analysis of the long-term consequences.
BHP is battling a longer-than-expected commodities rout which has eaten into its balance sheet. The miner recently slashed its dividend 75 per cent, while reporting its first loss in more than 16 years.
Mackenzie will also warn that a Leave vote would wear down the UK's economic, political and diplomatic clout.
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"The in and out campaigns are really about unilateralism versus internationalism. Most businesses support the EU and internationalism," he is expected to say.
"For Britain to wield the economic political and diplomatic capital it has historically enjoyed, we must vote to Remain."
MacKenzie previously put his name to an open letter backing the remain camp and prime minister David Cameron's reforms in Europe.