Absa denied rumours on Thursday that it is planning mass retrenchments to cut costs.
Employees affected by its restructuring process, were being given the opportunity to apply for positions across the group, it said.
It was responding after Solidarity challenged Absa CEO Maria Ramos to confirm or deny rumours that "large-scale" retrenchments were on the cards.
"This comes after a very reliable source close to Ramos contacted Solidarity a few weeks ago, claiming that Absa was planning to perform large-scale retrenchments," Solidarity deputy general secretary Dirk Hermann said in a statement.
He alleged that Barclays had given the instruction for the retrenchments as a cost-cutting measure.
Finance union Sasbo, which represents about 20,000 workers at Absa, has vowed to fight any possible retrenchments.
"At no time during the consultations did the bank mention retrenchments, and it made a commitment that should there be any retrenchments they will consult with us," said Sasbo general secretary Comfort Duma.
"The union believes that this restructuring process will adequately be addressed."
Absa said it had ensured that all interested parties, including Sasbo, had been fully consulted about its restructuring.
"... [W]e will always strive to ensure that our employees remain a key focus for the group," it said.
Absa said that since 2009 it had "consistently indicated" that it was trying to improve efficiencies and effectiveness, while reducing duplication.
"Where the reorganisation of particular business units is necessary, we aim to minimise the impact on our people through effective processes to find suitable placement for these employees. In exceptional cases, this may not be possible."