Some 450 people with PPI claims said the bank told them their attempts to recoup their money were refused as the information had been disposed of under data protection rules.
Scotland's biggest payment protection insurance claims company, which submitted 1300 claims in 2012 on behalf of Clydesdale customers, maintained the bank was the worst to deal with in making the mis-selling claims.
Paisley-based Payment Protection Partnership, which has reclaimed almost £100 million for Scottish customers, claimed Clydesdale is the only bank to cite data protection laws in failing to provide customer records dating back more than six or seven years.
Dundee-based Beat the Banks revealed in yesterday's Herald it was being told by Clydesdale that records more than six years old had been destroyed under the Data Protection Act.
The Commons Treasury Select Committee is to be asked to investigate. Committee member Stewart Hosie, the SNP MP, described the allegations as deeply troubling. No regulator appeared to take responsibility, he said.
Richard Caplan, founder of Payment Protection Partnership, said: "We have had a massive problem with the Clydesdale.
"At one stage we had to go to the Information Commissioners Office to get them to respond at all to SARs [subject access requests]. The bank doesn't even speak to us because of what we have been doing. We have good relationships with all the other main banks."
He said the other PPI claims firms had experienced the same difficulties. Mr Caplan said that in common with Beat the Banks, his firm could usually obtain records from other banks going back 15 years or more.
Former Clydesdale banker Mike Begg, founder of Beat the Banks, has evidence to show that on several occasions the bank has been able to produce old records which it earlier denied having.
According to Mr Begg, it is "impossible for the bank to destroy everything after six years" and the bank "just does not want to give it out".
Payment Protection Partnership said it has similar evidence. Claims handler Emma Davidson said: "We have hundreds of examples of clients who have received loan agreements dating back further than seven years previously, yet we have the same amount whose information is said to have been destroyed."
Clydesdale's standard response to applications for pre-2006 records is that it is unable to supply documentation as the paperwork had been destroyed in line with the fifth data protection principle.
The Information Commissioners Office (ICO) is unable to look at the issue except on a case-by-case basis.
The Financial Conduct Authority has said organisations may have a policy of keeping records for six or seven years, but must still co-operate with any complaints or claims.
Mr Hosie, MP for Dundee East, said: "It is bad enough for consumers to have been mis-sold products in the first place but if these allegations are true, that they are now unable to resolve these difficulties through information being withheld, it is deeply troubling.
"I am also extremely concerned that neither the Financial Conduct Authority nor the ICO seem to be responsible for ensuring this information difficulty is resolved, and I will raise this matter at the earliest opportunity with the Treasury Select Committee."
Clydesdale Bank said it was reviewing its PPI complaint-handling policy, including this matter. It added: "We fully recognise our obligation to provide a fair and comprehensive PPI complaint handling process which is not constrained by time period."