Unite national officer Dominic Hook has welcomed the Barclays chief executive's promise of a "culture shift" at the bank.
However, Mr Hook said more progress needs to be seen to address the gap between the highest paid and lowest paid employees, which he called "huge".
"It's shocking but true that the starting salary at Barclays is just £13,500 a year, making some workers at the bank eligible to claim tax credits", he added.
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Janet Ajao said in a statement: "I do not condone his actions nor support the beliefs he held that led to him committing this atrocity."