In a report for clients to be issued next week, BlackRock said Scottish independence would bring “major uncertainties, costs and risks” but a mass exodus of businesses from Scotland is unlikely.

The impact would mostly be felt by Scotland, but would also have a knock-on effect on the UK, the paper argued, according to the BBC.

It said a currency union between an independent Scotland and the rest of the UK “looks infeasible” and would “bring risks to both countries”.

The asset manager suggested the best option for Scotland would be to launch its own currency.

The company said oil and gas are critical to Scotland’s finances but fiscal spending based on specific oil revenue projections is “uncertain and probably unwise”.

It also suggested banks and insurers would face pressure to move headquarters to a “stronger fiscal state with a more certain regulatory backdrop”.

However, the report added: “A wholesale exodus of staff and operations would be unlikely, given Scotland’s cost advantage over London and other locations.”

A number of Scotland-based asset management firms have been creating contingency plans in the event of a a ‘yes’ vote in the 18 September referendum.

Standard Life’s chief executive Davish Nish said the group will consider relocating its operations if the Scottish people vote to leave the union.

Alliance Trust has begun registering companies in the UK to give it the option to transfer business activities as a precautionary move.