The chief executive of the City watchdog is at the centre of speculation that he has thrown his hat into the ring in the race to succeed Simon Case in the civil service’s top job.
Sky News has been told by a number of sources that Nikhil Rathi has expressed an interest in the cabinet secretary role.
It was unclear on Monday evening whether Mr Rathi had made it through to a list of about nine contenders who were due to be interviewed for the post last week and this.
The FCA and Cabinet Office both declined to comment.
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Mr Case announced in the autumn that he would step down at the end of the year on health grounds, following months of speculation about his future.
Last week, The Guardian reported that Oliver Robbins, the former Brexit negotiator, was on the longlist of candidates, and described him as the “probable favourite”.
A number of Whitehall departments’ permanent secretaries are also on that list, including Dame Antonia Romeo at the Ministry of Justice, and Sarah Healey, her peer at the Ministry of Housing, Communities and Local Government.
Mr Rathi has significant credentials for the role, having served as private secretary to both Tony Blair and Gordon Brown during their respective stints as prime minister.
He also spent nearly a decade in senior Treasury posts, including as head of its financial stability unit and as director of its financial services group.
In 2014, he joined the London Stock Exchange, becoming its chief executive in 2015.
Even if Mr Rathi is not in contention for the cabinet secretary role, the Treasury is expected to need to begin a search for his successor next year.
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Mr Rathi reaches the end of his first five-year term next September, and is considered to be very unlikely to seek a second term in the job.
During his time at the FCA, he has had to contend with an often difficult relationship with the government, with public rows about its enforcement regime and approach to economic growth punctuating his tenure.
In her speech at the Mansion House last week, Rachel Reeves, the chancellor, said that regulation of the City after the banking crisis had gone too far, and that watchdogs now needed to “regulate for growth”.