Conservative party co-treasurer Michael Spencer runs the firm which issued a profit warning last month.
A total of 114 traders and analysts will be hit by the cutting of the majority of its unprofitable cash equities business.
The business will have lost £25m in the financial year to the end of this month, ICAP said.
But the company is keeping its cost execution-only cash equities businesses in London, Brazil and the US, while shedding the rest.
Spencer said: "We have made a series of significant investments during the past ten years, which have successfully expanded and diversified our business.
"However, while a number of our cash equities businesses are performing well, the expansion into full service agency cash equities in Europe and Asia has failed to match up to our expectations. After a thorough review we have therefore decided to withdraw from the full service offering."