Britain’s financial watchdog has fined a former senior official at JPMorgan bank £793,000 (€1 million) for failing to be “open and co-operative” over the $6.2 billion losses racked up in the “London Whale” trading scandal.

Achilles Macris was head of JPMorgan's Chief Investment Office International in London, and manager of Bruno Iksil, the financial derivatives trader known as the London Whale for the size of his transactions.

Between March 28th 2012 and April 29th 2012 Mr Macris did not inform regulators of concerns about the bank's synthetic credit portfolio, and as a result he failed to meet the standards expected of an approved person, the Financial Conduct Authority said in a statement on Tuesday.

Mr Macris responded that the fine was a “major climbdown” by the FCA, having spent four years fighting to clear his name.

He has already challenged the watchdog for saying in an earlier, separate action against JPMorgan, which has since been settled, that he had deliberately misled the regulator.

“Today the FCA has finally accepted that this allegation against me was utterly wrong,” Mr Macris said.

“Now that the FCA has accepted that I did not deliberately mislead it, I have decided not to prolong what has been a drawn out and burdensome process and have settled with the FCA, on the basis that there is no prohibition on my working in the regulated sector,” Macris added.

JPMorgan declined to comment on the fine.

The FCA said it had been told at the end of March 2012 that the London Whale’s losses totalled $200 million.

But a few days later the regulator said it read in the Wall Street Journal that mark-to-market losses totalled $412 million in a single day.

The regulator spoke with Mr Macris and other JPMorgan staff during a 20-minute telephone at 5pm on April 10th about the article, but he was still not open and co-operative, the FCA alleged.

Mr Macris and other senior managers had put together “speaking points” to share with the bank’s communications team that were “intended to reassure recipients that the London Whale media reports were inaccurate,” the FCA said.

Mr Macris could have told the regulator that the portfolio had potentially suffered year-to-date losses of more than $1 billion on the actual day of the call, the FCA said.

During the call Macris also allowed the regulator to be told “inaccurately and without contradiction” that value-at-risk, a key metric, had been slashed because of hedging, the FCA added.

“A failure to communicate openly with us can affect the well-running of markets and cause unnecessary harm to investors, especially in times of financial stress or crisis,” said Mark Steward, the FCA’s director of enforcement.

“Regulators need open communication with firms so that better decisions can be made sooner. Mr Macris should have explained the position more squarely, especially when he knew the synthetic credit portfolio’s losses had worsened,” Steward said.

Without the FCA agreeing to a 30 per cent discount for settling at this time, Mr Macris would have been required to pay a fine of £1.1 million.