If a client's complaint is rejected, however, he is then told by the bank to seek independent advice.
The banks' agreement with the Financial Conduct Authority, the private nature of which was highlighted by BBC's Panorama on Monday night, allows them to appoint external reviewers and devise their own processes.
After 15 months, only 32 of almost 30,000 cases have been concluded.
Now Veritas Treasury, a Glasgow-based consultancy set up by former Bank of Ireland banker Scott Cowan, has said banks are discouraging customers from seeking support in the review process, whilst deploying £1000-a-day bankers and up to two lawyers across the table.
Edinburgh law firm MBM Commercial has already warned that banks have "a series of set questions aimed at eliciting material which will enable them to exclude the customer from the review and so block any redress".
Mr Cowan said: "In their letters, banks are saying you do not need expert advice for the review.
"But in letters saying 'you are not getting any redress', banks say 'you should seek expert advice'."
He said one client had contacted him on the eve of a meeting at his home, involving two lawyers and a banker, which was to be recorded.
"In any other walk of life, you would not want to go into a recorded meeting with two lawyers without getting some advice.
"I feel uneasy about the review process because it is the exact antithesis of PPI - the customer has to identify exactly what was wrong with the sale and what the bank should have done, though he didn't understand it at the time."
Mr Cowan said even where SMEs had been sold a 'category A' exotic swap product, supposed to trigger automatic compensation, months were elapsing with no redress being approved.
On the exclusion of more than 10,000 so-called "sophisticated" customers from the review process, also highlighted by Panorama, Mr Cowan said he had a number of clients who fell outside the review because their loan had been just above £10m.
He said: "It sounds a big sum but for some people who have been involved in business for a long time, and the particular loan might happen to be £10.5m, it doesn't mean they necessarily have a grasp of complex derivatives."
Panorama suggested banks which mis-sold swap products could end up being fined by the Financial Conduct Authority.