A US firm that routed business through a Bermuda subsidiary to “fleece” clients out of millions of dollars of extra fees has coughed up more than $150 million in fines in America.

The Bermuda arm of ConvergEx, a leading transactions services provider, booked nearly $13 million in trading profits from clients after it sent false statements to clients to hide its overcharging.

ConvergEx admitted its staff had repeatedly overcharged investors, including pension funds and institutional investors, through hidden fees.

Two former ConvergEx employees, Jonathan Daspin, the head trader of the now-closed Bermuda arm and Thomas Lekargeren, a sales representative from a different part of the company, pleaded guilty on Wednesday to wire fraud and conspiracy after cooperating with a major inquiry by the US Department of Justice and the Securities and Exchange Commission (SEC).

The SEC said that ConvergEx routinely routed orders to its Bermuda affiliate that executed the trades by marking up or marking down securities that caused some clients of the firm to pay more than double in fees.

The SEC said: “The offshore affiliate often consulted with the client-facing brokers to assess the risk of customer detection before taking the extra money on top of the disclosed commissions.”

Mythili Raman, acting head of the US Department of Justice criminal division, added that the firm “engaged in a concerted and coordinated effort to fleece its clients by charging them millions of dollars in unwarranted fees — which ConvergEx called ‘trading profits’ or ‘spread’ — and then concealing those charges from its clients through a pattern of deception.”

The Department of Justice said that Mr Daspin created false reports that were sent to customers to hide the deception.

Ms Raman added: “ConvergEx’s lies were repeated, deliberate and came in many different forms.”

The ConvergEx parent firm, as part of the settlement, paid $43.8 million and signed a deferred prosecution agreement with the Department of Justice to avoid criminal charges.

It also handed over a total of $107 million to the SEC and admitted wrongdoing to settle related civil charges.

A spokesman for ConvergEx said: “The overwhelming majority of ConvergEx’s equity execution business clients and customer orders were not affected.”

The firm added that the trading company had closed its Bermuda office and was given credit for its cooperation into the investigation by the US authorities.

The Department of Justice said Daspin “instructed a sales trader while creating a false report to ‘please put all prints in one spreadsheet in the least friendly format ... if possible take this out of spreadsheet format and make a PDF — or put this in picture file or something tricky to manipulate’.

In another incident, Daspin told an executive: “We need to be creative putting something together as did not have time and sales for the price given. Fyi.”