Biba rallied support this week from disgruntled members over the FSA's "misguided" plans to cut back the regulatory requirements for direct insurers.
The regulator proposes to remove the requirement for insurers to provide status disclosure, and a demands and needs statement to retail customers.
Biba is now urging brokers to copy and sign a template letter which claims the plan will lead to confusion amongst consumers.
Steve White, Biba's regulation and compliance manager, said: "We have been inundated with enquiries from brokers looking to complain to the FSA over these plans. I would expect them to receive hundreds of copies of the letter."
White also said Biba had been in talks with consumer groups over concerns that the plan would be damaging to the public. He added: "The level of response has been very pleasing. It will be difficult for the FSA to ignore such widespread concern."
Meanwhile, the IIB has also urged the FSA to drop the proposals, recommending it re-consults on the rules on status disclosure and demand and needs statements.
IIB director general Andrew Paddick said: "The current direct dealing non-advised sale status disclosure requirements are grossly inadequate and not robustly provided at the critical initial point of contact.
"It is simply too late putting this in documentation after a risk may have incepted."