The review of interest rate swap agreements (IRSAs) sold to small businesses is taking so long many victims risk being time-barred from taking legal action, advisers have warned.

It is six months since the Financial Services Authority (FSA) announced a review of all sales of swap-linked products, but 150 pilot case reviews by KPMG and Deloitte on behalf of four banks are yet to be completed.

After that, up to 40,000 cases will need to be processed by the banks, with the FSA promising independent scrutiny.

Campaign group Bully-Banks, which is to hold its first Scottish conference in Glasgow, says trust in the pilot case assessments is critical to assure businesses they do not need to resort to the law – particularly as the six-year time bar on litigation will soon overtake thousands of businesses that were sold their loans in 2007.

A further obstacle awaits businesses south of the Border, where reforms will bring England into line with Scotland in making it harder for successful claimants to recover their business losses by making them foot the bill for insuring against losing the case.

Bully-Banks spokesman Paul Adcock said the group had advised members in danger of becoming time-barred to instruct solicitors and formally begin litigation.

Mr Adcock said: "There is a high degree of sitting on the fence at the moment. People just don't know what 'fair and reasonable redress' will mean."

He said the pilot case assessments should be made fully public.

He said: "If you don't want people to go to court, they have got to have full confidence in the scheme."

Meanwhile, the NAB Customer Support Group is seeking to raise several hundred thousand pounds to submit a "test case" to the courts on the legality of swap breakage fees. Bully-Banks is hoping to secure a meeting with Clydesdale Bank to press it to reverse its decision not to include its widely-sold "fixed-rate loans" in its review of past swap-related loans.

Abhishek Sachdev at Vedanta Hedging, an expert witness to the Treasury Committee who has submitted an analysis of the products to the regulator, says they have breakage fees which vary daily, showing their link to an underlying derivative.

A large swathe of Clydesdale fixed-rate borrowers, meanwhile, has been hit by a double whammy, trapped by breakage fees but finding their loans transferred to National Australia Bank in preparation for repayment after Clydesdale left commercial property lending last July.

Giulio Girasoli, who started the Little Flowers nursery at Renfrew in 2006, was offered a 15-year loan in 2009, fixed for five years, and was told in June 2011: "We continue to be impressed by the business you have built up from a standing start to the success it now is, we would be pleased to consider funding requests."

But 13 months later in July 2012 he was told his loans were transferring to NAB and would not be renewed when they expire.

Mr Girasoli has repaid property-related borrowings but now faces rebanking the loans over the freehold of his nursery.

He said: "The other banks are not too keen to come in and take up the slack, and the politicians aren't doing anything.

"It is a very worrying time for the west of Scotland, it is driving down property values because a lot of Clydesdale customers are having to shift stuff very quickly."

Property revaluations are forcing many businesses into breaching bank convenants, triggering demands for repayment, Clydesdale customers told The Herald.

Mr Girasoli said: "People are frightened to speak up. I have got a smashing business, but it is getting choked at birth."

Clydesdale Bank has said : "NAB is committed to maintaining constructive dialogue with customers throughout the remaining loan term."

It has denied that there will be any significant impact on the Scottish economy.