Businesses campaigning for redress from National Australia Bank over the alleged mis-selling of swaps embedded in UK business loans have given a taste of their tactics at a Customer Support Group conference in Aberdeen last week.NAB's Clydesdale Bank subsidiary promoted tailored business loans before the financial crisis at rates that many customers now saw as un-commercial. The break costs on the loans were a particular source of angst.Edinburgh commercial barrister Iain Mitchell told the conference the European rules covering contracts for difference fell within the Markets in Financial Instruments Directive.Mitchell argued the banks mis-sold tailored business loans on a massive scale, based on the belief that they were protected by the Financial Conduct Authority's Conduct of Business Sourcebook rules."The bank thought that they were protected by execution-only contracts and did not read COBS or MiFID," Mitchell said."Product Swaps are contracts for differences, which are essentially gambling contracts and are simply unenforceable. This needs to be tested in the Supreme Court," he said.Michael Dempster, professor emeritus in statistics at the Centre for Financial Research at Cambridge University, told the conference embedded swap mechanisms in fixed rate loans were complex financial derivatives."The banks are rolling forward losses by the use of swaps which are mispriced, massively overpriced, benefiting only the bank," Dempster said.Liberal Democrat MP and Treasury Select Committee member John Thurso advocated a "super complaint" to financial regulators.The Customer Support Group published a summary of the arguments of its speakers.