TSB has called in IT specialists to help resolve its digital banking crisis after the bungled upgrade to a new IT system last weekend.
The challenger bank used its first quarter results announcement, which showed a slump in pre-tax profits, to say IBM had been recruited to try and resolve continuing "performance" problems with the new servers.
The team will report directly to TSB's under-fire boss, Paul Pester, the lender added.
It said all overdraft fees and interest charges for April would be waived for its retail and small business customers, on top of its commitment to ensuring no-one was left out of pocket by the debacle.
TSB tweeted overnight that it had taken its digital banking services offline for repair work over four hours.
It suggested access had returned by 4am.
It was the second time the bank had carried out such a fix, which it described as "fine tuning", since its troubled upgrade.
TSB has been limiting login access to its platforms to prevent a deluge of angry customers crashing the platform through high traffic volumes.
There have been a growing number of customers reporting desperate circumstances – a result of not being able to access their funds since last Friday in many cases despite chief executive Mr Pester's insistence that services were "up and running".
One user, TroysR_Us, suggested he had been unable to buy food while others said they were unable to pay bills and even their staff.
Mr Pester said on Wednesday evening that the "engine room" of the bank was running as it should – with everyday services for the vast majority of its total five million customer base running smoothly.
That included, he said, direct debits, standing orders, payments including salary credits, and transfers going in and out of accounts.
But Mr Pester added that he was truly sorry for continuing problems with the digital platforms – used by 1.9 million – admitting it was not functioning as it should be.
TSB had warned customers it would be switching to new servers at the weekend – a consequence of its move from technology used by its former owner Lloyds.
According to The Times, consultants raised concerns in 2015 – when TSB was bought by Spanish bank Sabadell – that TSB had not set aside enough money to ensure a smooth transition to new servers for what was an "incredibly complex" project.
TSB's results statement was headlined: "we're putting things right".
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