The FCA had more than 500 cases open at the start of April, which is nearly 100 more than the same time last year.
According to its annual report, the regulator had a record 504 investigations open as of 1 April, compared with 410 the year before, as the Financial Times first reported.
Of that caseload, 85 cases are looking into suspected financial crime and 75 are focused on insider dealing.
The FCA received 13,309 complaints in 2017-18 from victims of pensions scams, investment and insurance fraud, boiler room schemes and unauthorised collective investment or deposit taking business – a record number.
Data from the FCA annual report analysed by law firm Linklaters showed the amount of time criminal cases were taking to conclude had almost quadrupled since 2015.
The average length of all criminal cases was 16.3 months in 2015. It jumped to 58.2 months in 2017/18.
The total value of financial penalties issued by the regulator dropped by 78% in the same time frame to just £69.9m.
The FCA said the number of cases – criminal or otherwise – it had received in the last year had risen by 14% and that criminal cases typically took longer than others.
The regulator said its move to new offices in Stratford would “enhance its ability to deal with cases efficiently” in 2018-19.
The annual report also showed an increase in staff employed by FCA – from 2,511 in 2014 to 3,739.