Adair Turner, former head of the Financial Services Authority, has condemned Credit Suisse's $17bn AT1 bond wipe-out and the overall supervision its sale by regulators to UBS last week.
The new write-down was one of the first times this post-2008 regulation has been used, and the readjusted of the capital structure has bee hotly critiqued since the sale.
UBS bought Credit Suisse for $3bn on 19 March after its delayed annual results saw its share price decline dramatically and authorities stepped in to prevent the Swiss lender collapsing.
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Turner, who chaired the FSA from 2008 to until it was abolished in 2013, said to The Times that it had been an "odd thing" for the Swedish authorities to put Credit Suisse shareholders ahead of bond holder in the buyout deal.
The bank's shareholders were deprived a of a vote on the takeover, and received one share in UBS for every 22.48 shares they owned.
Turner also levied criticism as the regulators, claiming they had failed to get a "grip" on the scale of the issue at Credit Suisse before the situation escalated.
In his interview, Turner said: "I think it would be better to do it differently."
"It is not obvious to me why, if you believed you had got to wipe out the bondholders, you wouldn't have wiped out the equity holders."
The former chair added: "I think we should look carefully at the procedures and we should try to get to a situation where in all future such resolutions, we stick to the well-defined appropriate order of priority, which is, first of all wipe out the equity owners then wipe out subordinated debt to the extent required."
