By Emma Rumney
LONDON (Reuters) - A workers union said it had warned Britain's TSB about possible problems with the roll-out of its new IT system, which locked thousands of customers out of their accounts and plunged the bank into crisis when it launched in April.
TBU, a union representing over 4,000 TSB staff, said the outage could have been avoided had the bank listened to its members.
Its assertion came in a series of letters and newsletters from TBU, published on Thursday by Britain's influential Treasury Committee of lawmakers, who said earlier in June they had "lost confidence" in CEO Paul Pester over the crisis.
In one letter, addressed to the committee and dated earlier in June, Mark Brown, general secretary of TBU, said the union "can't understand" why the TSB board did not take its concerns seriously.
"Had they done so TSB might not be in the mess it is in today," he wrote.
The problems at TSB arose when the bank tried to migrate customers onto a new IT platform, developed by its parent, Spain's Sabadell.
In the letters and newsletters in the run up to the migration, TBU highlighted a number of concerns, including relating to the testing of the system and training of staff.
A TSB spokeswoman said that the coordination and testing of the system was led by Sabadell's technology subsidiary Sabis, whose testing regime was now the focus of an investigation into the root causes of the problems.
"We would never have moved across to the new system if we didn't believe we were ready," she said.
The Treasury Committee also published a letter from TSB Chairman Richard Meddings, who said Pester continues to have the board's support following the committee's call for them to consider whether he should stay in his job.
The bank had received 107,846 complaints by June 18 - compared to 76,000 in all of 2017 - Meddings continued, adding TSB had already hired an additional 105 complaint handlers and would add another 225 starting in July.
He said a report into the outage by law firm Slaughter & May, commissioned by TSB, would be published with commercially sensitive information redacted.
"TSB is now functioning at, or close to, normal for the majority of TSB customers," he wrote.
(Reporting by Emma Rumney; Editing by Alexandra Hudson)
