Difficult issue. It is out of remit for a gas safe engineer to attempt to fit a bonding connection, as he is (usually) not also an electrician.
There is NO LAW at all which enforces a PIR on change of tenancy - that's simply good practice, and a recommendation but not law.
IMO - should the Gas Safe guy find there is no bonding to the incoming gas, or on the boiler (most of which are connected either via a three pin plug top or into a wiring centre via a spur or 20A DP switch will have an earth reference.
Certainly, the fault will lie with the landlord, who should be aware of the importance of such a connection, and should see to it with haste. As to why it was not reported on the EIC - or PIR when he bought the property?? There is an argument there.
That argument is that it is UNLIKELY that the landlord has taken ALL REASONABLE STEPS to ensure the safety of his tenants whilst in his property. In order to establish he has done so, he would be required to produce at least one of either EIC, or a PIR less than five years old. Arguably, he needs also to satisfy himself at the outset of each tenancy agreement that he has, similarly, taken all REASONABLE steps to ensure tenant safety. It would seem that at some level he has NOT, and therefore, would probably be liable if his tenant was electrocuted as a result of touching an energised gas pipe.
Alternatively, he would have to prove that he DID have an electrician attend, who had confirmed the installation safe - most usually by means of a PIR. If he has a PIR and the missing bonding is not noted on there, then the electrician can be considered liable for either not doing his job properly, or for failing to identify and notify the landlord of a potentially dangerous installation.
If the PIR has been done, and also DOES note the missing bonding, the onus once again falls on the landlord, but ALL OF THIS only applies if something actually happens which puts tenant safety at risk. That, IMO is where the whole thing falls down.
I've said before that issue of a liability insurance cert should depend upon issue of a correctly completed Gas Safety, Electrical Safety and Water safety report. I still see no reason why that cannot be the case. Change of tenancy should result in minor inspection reports, which carry out and report visual, and essential functional changes, with a full report being compiled annually, for issue of the insurance cert.
We are, sadly, a long way from that.
