BP's chief executive Bob Dudley has warned that major companies may divest billions in future investment away from Scotland because of the uncertainties the country's independence would mean for business.
Dudley said that "all businesses have a concern" about the in/out referendum, which takes place on 18 September 2014.
"It does not seem the right thing to me for the country [Scotland] to drift off. That's not a company view, that's from me," said Dudley.
However, he added that BP would be likely to pay higher costs in the event of Scottish independence and that uncertainty over the country's currency would not help billions of pounds in future investment.
"My personal view is Great Britain is great and it ought to stay together," said Dudley.
"There's enough uncertainty and talk about it and the questions raised. It would create extra costs for our business and we would have to have duplicate centres and do things, and again the currency question ... These investments they're big, they're underway and we want to see things develop. It depends on what tax regimes are there and it depends on currency."
Scottish people will vote in an independence referendum in September this year and will be asked the straight "yes/no" question: "Should Scotland be an independent country?"
Meanwhile the pro-independence Yes Scotland campaign dismissed the BP chief's remarks and said in a media statement: "with independence, the continued use of sterling has the overwhelming support of the people of Scotland and the public in the rest of the UK."
UK Chancellor George Osborne recently said that a currency union based on the pound would be "unworkable."
He also added that Dudley's comments highlighted the concerns of many business leaders which have a major stake in creating jobs and tax revenues for Scotland.