A spokesman for IG confirmed FD's appointment but declined to comment further.
IG Index was founded as IG Group in 1974 by Stuart Wheeler and was first floated on the London Stock Exchange in 2000. The firm was subsequently taken private in 2003 after Wheeler sold his stake and CVC Capital Partners backed a management buyout led by chief executive Nat le Roux.
As well as spread betting, IG Index's subsidiary IG Markets acts as a market maker in financial derivatives.
Subsidiary binarybet uses a system whereby punters can change their bets before a sports event has finished and bet on fixed returns for specific outcomes.
IG Index has around 15,000 clients. In the year to May 2004, it made a pre-tax profit of £23m on turnover of £48m.