TSB has pushed back its target for about half of its senior jobs to be held by women by up to five years.
The bank had originally pledged to meet the target by next year, but it now says it should do so before 2025.
In fact, TSB has moved further from its target as it had 41% of women in senior roles in 2017, but only 38% this year.
The bank has, however, beaten the government’s target for 33% of boards to be made up of women “with a board that is 36% female”.
“TSB takes gender diversity very seriously,” a spokesperson told the BBC.
“We set an initial stretching target for between 45 to 55% of our senior roles to be held by women by 2020.
“We’re currently at 38% and although we are making progress, we have revised our target.”
The bank said it was now tracking “interim targets” which it hoped to meet before 2025.
Tackling the gender balance was a challenge across the banking industry, but TSB was being transparent about changing its targets, the spokesperson added.
Earlier this year, TSB launched its Aspiring Women network to “improve the talent pipeline” to address what it says is a lack of female talent in banking.
It is also introducing inclusion training for managers, to remove unconscious bias and other related issues.
Companies have come under increasing pressure to close the persistent pay gap between men and women, which in part reflects the concentration of women in lower paid positions. The TUC says the reasons behind the lack of upward mobility for women include childcare duties and preconceptions about their roles.
TSB has had a difficult year and last week revealed which 82 branches it plans to close in 2020 as part of cost-cutting measures.
The closures are part of a plan by new chief executive Debbie Crosbie to save £100m by 2022. The bank said that 370 positions would be affected.
In November, an independent report into IT failures at TSB that left 1.9 million customers unable to bank online in April 2018, blamed the bank and its IT provider Sabis.