The news came two days after Man shocked markets by reporting clients had pulled out $2.6bn (£1.67bn) in assets in the three months to the end of September,
The group’s shares tumbled 25 per cent on the day.
While job cuts are taking place across the board, the majority are in fund administration and sales, although fund management and research are not seeing redundancies, the source said.
The cuts, which will take place by the first quarter of 2012, were already underway before Wednesday's trading statement, the source added.
Man had originally been planning around 200 job cuts after last year's takeover of GLG, which was bought for $1.6bn to boost assets and diversify Man's business away from computer-driven funds.
Chief operating officer Emmanuel Roman, seen by some to have built up a power base to rival that of CEO Peter Clarke, has been in charge of the integration of the two companies.
Man Group declined to comment.