I doubt you need primary legislation to fix that. I expect that secondary legislation giving direction to Ministers and regulatory bodies to ensure that fines are commensurate with the level of offending would be helpful. I suggested that the level of fines by these professional bodies supervisors and by HMRC is just not commensurate with the financial advantage of taking part in these transactions.
Indeed, if you are a solicitor, and someone complains to the Solicitors Regulation Authority about you because you have been holding up a transaction, that will still be investigated. You will still incur quite a discomfort in responding to that investigation. That is quite a powerful incentive just to go along with the transaction, whereas the fine you might receive for having gone along with a transaction that you should not have could well be less consequential for you. That needs to be addressed.
Fines wielded against trust and company service providers by HMRC, for example, are pitifully low. We were told by the trade body that its experience of fines imposed by HMRC on trust and company service providers was typically no more than £1,000.