Britain's Inland Revenue last year won a landmark case obliging Barclays, a British high-street bank, to hand over the bank details of hundreds of thousands of offshore accounts held by British residents.
Meanwhile, parents are "just crossing their fingers and hoping somebody will budge, " said Evie Gurney, the director of high-school placement at Bank Street School for Children.
The group confirmed it also plans to extend its legal services across all 330 high street branches of the Co-operative Bank and Britannia Building Society.