An independent Scotland would be a big success, according to the head of the country's largest asset manager.

Martin Gilbert, chief executive of Aberdeen Asset Management, said Scotland could prosper regardless of the outcome of the referendum next week.

Gilbert said the Scottish government's preferred option of a formal currency union between an independent Scotland and the rest of the UK would be "highly likely", despite it being repeatedly ruled out by the three main pro-union parties.

Scotland could also benefit by refusing to take on its share of the UK national debt if denied a currency union, he added.

He told the Press and Journal newspaper: "I think an independent Scotland would be a big success."

He added: "Most sensible people now accept that Scotland would be prosperous with either outcome in the current constitutional debate.

"A sterling union would be both desirable and highly likely whatever is said in London now. Sterlingisation, that is keeping the pound come what may, would be a pretty good option.

"Low or no debt would be the position if an independent Scotland were denied access to Bank of England financial assets, and that would leave the newly independent country in both budget and balance of payments surplus – not a bad start."

The Scottish finance secretary, John Swinney, said the comments were a "significant intervention".

He said: "As Martin Gilbert says, an independent Scotland can and will be a big success. With the powers of independence we can support our economy and ensure continued economic growth."

Swinney also welcomed comments from Sir Angus Grossart, chairman of Noble Grossart merchant bank, who suggested in the Financial Times that the impact of the referendum on the markets had been "severely overstated".

He said the intervention of Grossart, alongside supportive comments from Prof John Kay, from the London School of Economics, gave some "very welcome perspective".

"Scotland is one of the wealthiest nations in the world, richer per head than France, Japan and the UK, and with the powers of independence we will use that wealth to ensure all of Scotland will thrive," he said.