US investment bank Jefferies is being investigated by the Financial Conduct Authority (FCA) over claims senior executives forced analysts to change some of their reports in a bid to win clients.

In a legal claim submitted to a London employment tribunal, Milan Radia, a former leading analyst at the firm, alleged some of his former superiors forced him into changing a report amid pressure from a client.

According to The Times, Radia, who worked as managing director at the US bank, added he was also asked to attend float pitches, a clear contravention of market rules.

The bank allegedly also allowed bankers to interview analysts that were looking to join its research division.

According to Radia, Jefferies also breached rules over the permitted use of equity research in a bid to secure lucrative initial public offerings (IPO).

The New York-based lender paid its equity research analysts for "their specific work on winning IPO and other investment banking transactions", the tribunal was told.

One of Radia's lawyers told the tribunal that on 28 March this year the FCA notified the bank it would be subject to an official review over the claims, which has since begun.

Jefferies international chief financial officer Huw Tucker told the tribunal that he was aware of the City watchdog's investigation.

"We did have a board meeting with the FCA where they informed us of the investigation," he said, although he claimed he was not fully aware of Radia's allegations.

Radia, who spent 11 years at the firm, had previously brought another claim against his former employee, alleging discrimination based on disability. The former managing director had argued his bonus was cut after he returned to work following treatment for leukaemia, but his claim was rejected and he was subsequently dismissed by the US bank.

The tribunal said at the time that Radia "in a number of respects [...] did not tell the truth or misled the tribunal".

Radia has also alleged he was unfairly dismissed after he revealed the bank had breached research rules.

The tribunal was told the claim focused on a research report Radia wrote for Telectity, a data centre company formerly listed on the London Stock Exchange, and Moneybokers, a payments and money transfer firm which has since changed its name to Skrill.

Sam Neaman, representing Radia, told the tribunal his client had been asked to alter a report on Telecity after David Weaver, a former senior investment banker at Jefferies, had "succumbed" to pressure from the company.

Commenting on the trial, a spokeswoman for the US bank said: "As was the case with Mr Radia's first tribunal claim which he lost on all points, this claim has no merit and we are confident that we will prevail."

The case continues.