Brokers which left the IBRC carried on trading and simply became intermediaries.
But broker trade body the IIB has resisted the compulsory element which it regarded as bully boy tactics by insurers, and threatened legal action against it.
The GISC faced a humiliating setback this week when chief executive Chris Woodburn conceded that membership is almost certain to be voluntary for the next year.
Woodburn believes its failure to produce a rule book before March 1 would leave the fledgling regulatory body open to a legal challenge if it goes down the compulsory route.
March 1 is the start date of the new Competition Act.
The GISC board meets today to decide whether to press on with its original "empowered" route or to accept the organisation must be voluntary for at least a year.
During this time, GISC would seek approval to be compulsory from the Office of Fair Trading.
Woodburn doubts that the GISC will write a rule book in time, following the massive response to its second consultation document.
Among more than 300 responses, queries were raised about GISC's stance on training, professional indemnity levels, membership fees, the ombudsman scheme and a host of other issues.
"My view is that it is likely we will go down the voluntary route on a short-term basis," Woodburn said.
GISC board member, AiiB chairman Mike Slack, also said that he firmly believed the GISC would start out as a voluntary organisation.
Slack said: "I believe it will start as voluntary until it gets OFT approval."
The compulsory element of the GISC, provided by ABI members agreeing to cancel agencies from those brokers and intermediaries which did not join up, has been the thorniest issue since its inception.
It is one of the central planks of the GISC because the current statutory body, the IBRC, was widely regarded as a failure because as a voluntary body it lacked teeth.
Brokers which left the IBRC carried on trading and simply became intermediaries.
But broker trade body the IIB has resisted the compulsory element which it regarded as bully boy tactics by insurers, and threatened legal action against it.
"I knew they were going to try to jump the gun, but they can't make it mandatory because GISC has no power," Andrew Paddick, IIB director general, said this week.
Paddick also attacked the new body's record so far, saying: "It can't organise meetings, it's had problems with booking forms, there have been mistakes in documents. The whole thing is an absolute shambles."
Any delay could have major implications for the GISC's funding arrangements. The regulatory body originally had £2.2 million worth of funding. More than half the sum, £1.15m, came from brokers, while insurers provided £1.05m.
Mandatory membership was meant to provide GISC with the bulk of its revenue, and the delay to the timetable, if it does occur, could cause serious cash flow problems because many potential members may not now join.
Head of communications, Catherine Nicoll, said GISC had not ruled out making a second cash call to its backers, but no decision will be taken until after today's meeting..
A third consultation document may be created, although, that is likely to be agreed at today's meeting.
To try to promote itself as a voluntary organisation, GISC, which has no advertising budget, will seek to place articles in magazines, such as Caravan Weekly and Angling News.
