Speaking on the sidelines of the St Petersburg International Economic Forum, Dudley said: "It's not going to change exactly what BP does. We will respond.

"(But) my personal concern is the unintended consequences - no one is quite sure what will happen. I'm sure the pound will gyrate a bit. I think it will put the world into some period of uncertainty ... including for Britain. So, I'm concerned about that," he said.

(This version of the story was refiled to amend the headline)

(Reporting by Vladimir Soldatkin; Editing by Andrew Osborn)