Around 20 ex-employees, backed by a Surrey-based campaigning group, Freedom to Care, will demand a Treasury and Civil Service Select Committee inquiry into alleged training and sales irregularities before the conversion goes ahead.
Some 350,000 UK policyholders will receive cash or shares worth at least pounds 285 when the Australian-based group floats on the Stock Exchange next year. Policyholders in Australia voted in favour of the plans at a special meeting in Melbourne on Thursday.
The UK vote is expected to go through comfortably despite the protest, but not without further dissent.
Large number of endowment policyholders are angry that, under Colonial's rules, the windfall bonus may pass to mortgage lenders where the policies are pledged as security for home loans.
The Personal Investment Authority is currently investigating Colonial's training and supervision record, following allegations made by former manager Peter Smith.
Mr Smith is also suing for alleged victimisation after he blew the whistle on the group. His case has since been taken up by his local MP, the former defence secretary Tom King, and by Austin Mitchell, the campaigning Lab- our MP.
The PIA has been accused of dragging its feet, however. Following a leaked report, the watchdog has also come under fire for doing little to redress the pensions mis-selling scandal that has dogged the industry over the last few years.
Colonial denies Mr Smith's allegations.Reuse content