The group will send a questionnaire to its 14,000 members to identify examples of tax decisions by the Inland Revenue that could be challenged in the courts. It plans to identify a list of test cases by the end of the month.
The move follows the group's defeat last month when Court of Appeal judges ruled that IR35, which has been condemned by employers groups, did not breach European competition law.
Opponents argue that the IR35 regulations are unfair because they treat contractors as employees for tax purposes even though they receive none of the benefits of permanent staff, such as paid holidays and sick pay.
"We will take cases where there is a grey area and look to clarify them," said PCG spokeswoman Susie Hughes. "One point that the court agreed with us is that the case law goes back to the 19th century and has not kept pace with technology workers."
The PCG said it hopes to work in partnership with the Inland Revenue to clarify the regulations. "This is not a confrontation. It is to everyone's benefit to work together," said Hughes.