It depends on the circumstances.
And it's not necessarily either/or - it might be both.

Why must there be someone to BLAME ?

Can't you just do a thorough investigation and come up with a reason for the accident and a few ways to ensure there is no recurrence ?

Accidents are preventable, therefore someone had the ability to prevent!

Already carried out an investigation, and began to implement corrective actions....But, was asked by someone in management, if we could be held responsible (in terms of claims)...My experience of claims is zero...investigation flagged up fault on both sides...Seen this in a previous job, the minute someone knows the person who had the accident, isn't dead, they then start to think how much it will cost in claims

jon joe, was the accident 'foreseeable' i.e. was there an obvious risk, and was that risk not identified in the i) Contractor RAMS or ii) the site manager/PC RAMS?

BTW, I don't subscribe to the notion all accidents are preventable. Most accidents are preventable. All accidents would only be preventable if you had hindsight plus the powers of Superman!

Ray, yes, agreed, 'most' accidents are preventable. I rushed my response!
Also, John, yes, foreseeability is the test.

I'd therefore suggest, most accidents are foreseeable, preventable and failure, is a failure of responsibility. Who had responsibility is the question.

Something often only determined in court, should it get that far through the process!

1. Not sure what your getting at...Anyway, the Contractor was fixing something (wont go into detail), and he climbed into a small enclosure, which wasn't designed for a person to do so, and was injured...Foreseeability, as already mentioned, is something which I;ve failed to do, as when I asked the Maintenace team previously, about any abnormal practices, this wasn't mentioned, therefore it wasn't investigated, as I didn't see it as an issue

2. After investigation, Contractors were unsupervised, and after checking the Method Statements for this work, it doesn't mention doing it, in the way they did

Vulnerability to a civil claim is dependent on there actually being a claim - which has to be initiated by the person suffering injury or loss, and could be directed to any or many parties.

Then the claim can be contested by whoever is claimed against - but this is in the hands of company insurers, and small claims are often settled early as a cost measure.
As the burden of proof in civil matters is lower than criminal (regulatory) cases, even if gets to court the outcomes can seem perverse.

The amount of excitement generated at management level by civil claims is often disproportional. One should be grateful there has been no enforcement action, and focus more on any learning points.

I was taught years ago not to get over-excited by civil claims (reinforced by a helpful HSE inspector too) and certainly don't over-react to any civil court 'recommendations'. Give them due consideration, but they are not always helpful.

Trying to second-guess civil claims is not really a H&S practitioner job, but I guess management don't see the difference, so having a bit of an understanding of the process is useful.

Safety management for the compliance with legal standards and avoidance of events is the best line of defence against any action including civil claims, but if the worst happens - well that is what the civil and insurance systems are there for.