IG withdrew £160m from its loan facility just before the EU referendum result to ensure it could cope with the surge in activity.
Its new execution-only stockbroking service got off to a slower start, signing up 11,000 funded accounts since September 2014.
IG is also branching out into passive investments in a partnership with BlackRock, which Mr Hetherington said would launch within a few months, in a bid to offer more traditional wealth services to its trading customers.
These new projects, along with a salary review to try and minimise resignations in the firm’s London office, raised operating costs by 17pc to £241.5m during the year.
“Recent attrition levels in our London office have been too high, due to competition for the scarce skills we require to prosper. In response, we have increased some salary levels to help retain key staff,” said chairman Andy Green.
IG paid more than £10m in betting tax during the year on losses accrued by its spread-betting and binaries customers, double the duties paid last year.