A London-based pension insurance firm has passed up opportunities to invest in Scotland because of uncertainty caused by the independence referendum.

Mark Gull, co-head of asset and liability management at Pensions Insurance Corporation, which manages nearly £10 billion for almost 100,000 pension scheme members in the UK, said regulatory certainty is "very important".

"There are certainly Scottish things we have turned down because of their Scottish nature," he told the Financial Times newspaper.

"There is a small, but definitely material, probability that Scotland votes for independence, and if it does, that does not make it investment grade in our book. We want to have certainty."

He added: "It is probably going to be all right, but that is not enough for us. Regulatory certainty is very important to us."

But he said the company has recently invested in student accommodation in Edinburgh.

Gregg McClymont, the Labour shadow pensions minister, said the comments reflect fears among some businesses.

"It is deeply worrying that Scotland is already missing out on pensions cash as a result of business fears over the implication of a 'yes' vote in September," he said.

"Pension funds are absolutely central to the funding of key infrastructure projects in Scotland and the wider UK.

"When major investors warn about the risks from Scottish independence, we need to listen to them. Last week it was one of the biggest investors in the North Sea and a major supermarket, this week it's a multibillion-pound pension fund.

"Alex Salmond's failure to spell out his plan B on currency is a major cause of uncertainty for people who invest in our country and create the jobs that we need."

A spokeswoman for Business for Scotland said independence will be "fundamentally better".

"We believe that Scotland becoming an independent country will provide significant opportunities for Scottish businesses to become more entrepreneurial, confident, successful, ambitious and international, whilst simultaneously boosting the brand image of Scotland," she said.

"Scotland trading on its own terms, with the other home nations, and internationally, as a self-governing independent country will become one of the wealthiest and most progressive nations in the world."

Scottish Conservative finance spokesman Gavin Brown said the First Minister should reveal the fall-back plan for currency after independence. The Scottish Government says it is committed to sharing sterling with the rest of the UK.

Mr Brown said: "There are no guarantees whatsoever that the rest of the UK would enter into a formal currency union, so it's crucial the SNP says what it would do in that eventuality.

"This also highlights the risks and complications of a separate regulatory system. An increase in compliance costs would be viewed very negatively by the industry."