I have always recommended that the "owner" of an operation must be the person to give permission for dangerous work to be done that may affect their operations. By owner I mean the person with management responsibility and accountability. Thus I would expect a departmental manager to be the one to authorise work in their own department, unless it has plant-wide implications.

So far as competence is concerned, it is essential for the issuer to fully understand the implications of the work, the consequences of it taking place, the necessary precautions needed and able to judge whether these are being adequately specified.

I am less concerned with the law and more concerned with ensuring the work is done safely and not exposing the operation to uncontrolled risk.

Signing a permit is saying "I give my personal approval to this work being carried out in this place, at this time, in this way, with these precautions in place and take full responsibility for my decision".

I and other people are really concerned in what the law says so much so that people refuse to write permits, I need to clarify or have some guidance at the very least when a person is Liable or not. We can't operate with people refusing to write permits for the fear of being charged if something goes wrong, its a major concern to the permit writer and I can't find guidance anywhere

Mersey, if the permit writer is not sufficiently confident in their ability to make a good decision, they should not be authorising work. This should not be a paper-trail-creating exercise but a real tool to ensure safe work.

I too would refuse to sign a Permit if I didn't know enough about what was going on or was not fully convinced that the specified precautions wer adequate.

You asking people to be responsible and accountable. Do they have the necessary authority and abilities?

Anybody can be held liable for their own negligence, whether the new-start apprentice or MD and can also be subject to criminal prosecution if in breach of criminal laws. I suggest that signing-off dangerous work that later leads to an accident rightly puts the signer in the spotlight and the decision to allow the work would be closely questioned.

you may find the following useful in assessing the Individuals & Ensuring the Work Permit System is adequate
The Permit system should address the following points:

Whether staff have been sufficiently informed, instructed, trained and supervised to minimise a potential human failing during operation of the work permit system;
Whether the work permit system includes sufficient safety information, maintenance instructions, correct PPE and equipment for use;
Whether the work permit contains sufficient information about the type of work required (Equipment removal, excavation, hot/cold work, repairing seals, vessel entry, waste disposal, isolation);
Whether there is sufficient provision available to fulfil the requirements of the work permit system;
Whether the employees responsible for control of the maintenance work are identified within the work permit system and that the work is properly authorised by a responsible person;
Whether the work permit system is managed, regularly inspected and reviewed;
Whether all work permits are kept on file;
Human factors (stress, fatigue, shift work, attitude);
Whether sufficient precautions are taken prior to initiating a work permit (isolation, draining, flushing, environmental monitoring, risk assessments, communication, time allotted for the work);
Whether staff are aware of the type of environment they are working in during the operation of a work permit (flammable, corrosive, explosive, zones 0, 1 & 2, electricity supplies);
Whether the person responsible for operating the plant is aware of the type of maintenance involved and how long it is likely to take; and
Whether the work permit system involves a formal procedure whereby the maintained plant or equipment is handed back to operation.

If the person issuing the permit was authorised to do so and there was nothing obviously wrong with the permit process, then the liability for the accident would fall on the contractor for not following their own SSoW. Notwithstanding that, the client should ensure SFAIRP, that the contractor was competent and was carrying out the work in a safe manner.

As someone else has previously alluded, the material facts will often dictate where the liability lies - for example, if the client was required under their own h&s system to supervise the works, then the liability could fall to the client or both the client and contractor depending on the cause of the accident.