Because the RP is responsible for carrying out the the Risk Assessment. The person the RP employs to carry out the RA is not doing it on RPs behalf. He/she is assisting the RP.
Guidance note 1 is very clear on this 'For the avoidance of doubt, it is accepted that other persons may record the prescribed information at the request of, and on behalf of, the responsible person.' They are doing it on behalf of the RP.
The FRA belongs to the RP not the assistant.
I agree and Guidance note 1 seems clear on this too 'If a responsible person relies on a risk assessment carried out on their behalf by a person who is competent to carry out such a risk assessment, it may be a strong mitigating factor if the responsible person is prosecuted for an offence under article 32, although it will not relieve the reponsible person from criminal liability.'
I think the assistant would have no liability under the FSO.
Article 32(10) seems to have this covered 'Where the commission by any person of an offence under this Order, is due to the act or default of some other person, that other person is guilty of the offence, and a person may be charged with and convicted of the offence by virtue of this paragraph whether or not proceedings are taken against the first-mentioned person.' I take this to include a risk assessment that is not suitable and sufficient which is as relevant as a fire alarm engineer who does not maintain the fire alarm system to a suitable standard.
That may not preclude the RP from some form of civil action against the assistant but then the RP has to ensure that the FRA is suitable and sufficient.
And I agree with your interpretation here, however this is where I start to get a bit confused as Guidance note 1 seems to contradict itself and the FSO as it says 'For the avoidance of doubt, enforcement action is taken against the responsible person, not the contractor. A contractor may well be liable to the responsible person in contract or tort for a negligently carried out risk assessment, but that is outside of the scope of this guidance.'
How does the responsible person ensure that the risk assessment is suitable and sufficient. If I have hired a person who I consider to be competent, would I then be expected to get a third party in to make sure it is suitable and sufficient, or do I wait unitil the enforcing authority check it, which could be in many years time, if ever!
I may be looking at it wrongly or missing another part that is vital to how it reads, but it doesn't make much sense to me, help!!