In July, Andriesz told MPs and campaigners the FCA had been fully informed about other serious allegations he had made as long ago as 2018 and accused it of inaction.
The FCA told the BBC in July it had acted on his allegations and pointed to a supervision order it had issued based on his information.
But in Andriesz's view that amounted to little more than a regulatory "slap on the wrist" and made it harder to make a claim for whistleblower retaliation against BGC at tribunal.
Later that month, he told a meeting of the campaign group the Transparency Task Force the FCA was not fulfilling its obligations to the public and whistleblowers and merely "pays lip service" to the rules and regulations.
"It protects the institution and then exposes the whistleblower to extreme retaliation and devastation to their lives and families," he said.
The FCA told the BBC it was appointing a new non-executive director on its board, former Bank of England director Lea Paterson, to conduct a review into Andriesz's treatment and the FCA's handling of his whistleblower allegations.
An FCA spokesperson said: "We are very sorry to hear of Mr Andriesz's death. Our thoughts are with his family and friends.
"Since expressing our condolences, we'd asked Lea Paterson, who has just joined our board as a non-executive director, to review how we interacted with Mr Andriesz to learn any lessons for the future."
English (US) · 
Turkish (TR) · 