The ORCL is consulting lobbyists on how enforcement of the register, which was launched in March, should work in practice.
The Act provides for possible enforcement action against organisations that register a client but do not carry out lobbying work, as defined by the act. For example, an agency might register its client on the register to err on the side of caution but may not have carried out any lobbying work for the client initially.
The consultation proposes a number of interpretations of the Act and ways in which the Registrar might enforce compliance.
It seeks views on administrative errors, historical inaccuracies, signposting corrections, non-registrants, the makeup of the information notice that will be served to organisations and what criteria would be considered reasonable grounds for investigating an organisation.
In its response, the PRCA argued that treating the over-declaration of clients as non-compliance is inconsistent and at odds with the spirit of the legislation.
It said the ORCL should allow members to adopt approaches which protect their integrity and reputation and permit this additional disclosure.
Proposals also include provisions to investigate an organisation that "substantially" increases or decreases it client list and the PRCA said it was seeking reassurances that standard business practices in the industry were properly understood.
Francis Ingham, PRCA director general, said: "We cannot possibly treat the over-declaration of clients as some sort of offence: it would be a perverse interpretation of the Act and handicap an already limited Register. We urge our members to err on the side of caution on our voluntary Public Affairs Register, therefore over-declaration should be facilitated.
"Having facilitated voluntary disclosure for decades, the Office has to get the process right. Adding further twists and turns at this point would fly in the face of an industry which embraces transparency."
The APPC also responded to the consultation process.
APPC chairman Iain Anderson said: "We feel that the Registrar should be focusing most attention on those organisations that should be registered but have not done so and therefore continue to act outside the law. This risk-based approach should be used to best define the actions of the Registrar in relation to consultant lobbying and in allocating the resources of the Office."
A spokesman for the ORCL said it had not reached a view on whether over-declaration should lead to enforcement action and that it was the purpose of the consultation to "reach a view" on the interpretation of the Act.
The consultation ended on Friday and the ORCL is expected to define its compliance policy before the end of the summer.