Section 36 of the Principal Act is hereby amended by the addition of the following subsection:

"(5) Notwithstanding anything in section 62, where a claim is made against a person who is insured in respect of a liability alleged in that claim and the claim is not paid by the insurer by reason of its being set off in full against a sum owed to the insured by the person making such claim, the insured or any person representing or deriving title under him shall be entitled to recover from the insurers the amount of such claim."