Two British corporate giants have warned of the economic consequences of Scotland voting for independence next week.

BP’s chief executive, Bob Dudley, said that a “yes” vote in the referendum could threaten investment in the North Sea oil fields by firms such as his. “As a major investor in Scotland – now and into the future – BP believes that the future prospects for the North Sea are best served by maintaining the existing capacity and integrity of the United Kingdom,” he said.

The spending plans of a post-independence Scottish government would likely be heavily influenced by the amount of tax raised from North Sea energy extraction.

Meanwhile, the Edinburgh-based pension provider and insurer Standard Life reiterated its warning from February that it would relocate large chunks of its operations to England in the event of Scotland leaving the United Kingdom.

“In view of the uncertainty around Scotland’s constitutional future, we have put in place precautionary measures which would help enable us to provide customers with continuity” the firm said in a statement today.

In pictures: Politicians scramble for Scotland Show all 6 1 /6 In pictures: Politicians scramble for Scotland In pictures: Politicians scramble for Scotland Politicians scramble for Scotland Labour Party leader Ed Miliband speaks during a campaign meeting in Cumbernauld in Glasgow Reuters In pictures: Politicians scramble for Scotland Politicians scramble for Scotland British Prime Minister David Cameron gestures as he speaks during a visit to Scottish Widows offices in Edinburgh Getty Images In pictures: Politicians scramble for Scotland Politicians scramble for Scotland Scotland's First Minister Alex Salmond campaigns for a Yes vote in east Edinburgh, Scotland EPA In pictures: Politicians scramble for Scotland Politicians scramble for Scotland John Prescott campaigns for a 'No' vote in the referendum on Rutherglen main street in Glasgow Getty Images In pictures: Politicians scramble for Scotland Politicians scramble for Scotland Liberal Democrat Deputy Prime Minister Nick Clegg talks to the media during a campaign visit to the market place in Selkirk Getty Images In pictures: Politicians scramble for Scotland Politicians scramble for Scotland Better Together campaign leader Alistair Darling speaks to the public in Glasgow Getty Images