Professional negligence claims frequently involve more than one defendant. A commercial dispute may pull in the solicitor who advised on strategy and the counsel who settled the pleadings. A construction defect may draw in the architect who designed the scheme, the engineer who signed off the structural calculations, and the surveyor who monitored the works. When a court finds two or more professionals liable to a claimant for the same damage, it must decide how the responsibility is shared between them. That exercise is called apportionment, and it sits at the centre of most multi-party professional indemnity settlements.
Two statutes govern the exercise. The Civil Liability (Contribution) Act 1978, section 2, provides that the amount of contribution recoverable from one defendant by another shall be such as may be found by the court to be ‘just and equitable having regard to the extent of that person’s responsibility for the damage in question’. Where the claimant has themselves contributed to the loss, the Law Reform (Contributory Negligence) Act 1945, section 1, permits a corresponding reduction in damages by the court on the same ‘just and equitable’ standard.
Both statutes deliberately avoid a mechanical formula. The court has broad discretion. There are no fixed percentages, no tariff, and no presumption that responsibility is shared equally.
English courts assess responsibility along two limbs. The first is causal contribution: how far did each defendant’s conduct actually cause the loss? The second is blameworthiness: how morally culpable was each defendant’s breach? A defendant may be a small causal contributor to a large loss but have acted with striking recklessness; another may have been the proximate cause but merely careless. Both dimensions are weighed together.
In Downs v Chappell [1997] 1 WLR 426, the Court of Appeal emphasised that relative causal potency is a central strand of the enquiry. In Boehringer Ingelheim Ltd v Barr Laboratories Ltd [2011] EWHC 3038 (Ch) the court adopted a structured approach to apportionment, weighing each party’s role and conduct rather than reaching for a broad-brush split. The Australian authority ANI Corp Ltd v Celtic Explosives Pty Ltd [1996] APII 4-6 is also referred to in English submissions for the proposition that relative responsibility, not simple causation, is the master concept.
Apportionment is a fact-heavy exercise. Expert evidence is often decisive: an expert solicitor commenting on the standard reasonably expected of a competent litigator, an expert architect explaining what a diligent designer would have picked up. The court needs a clear picture of what each defendant was retained to do, what the standard demanded, where each fell short, and how those failures interacted. Documentary evidence — retainers, attendance notes, drawings, correspondence — anchors the analysis.
Case law shows a wide spread. In construction disputes an architect responsible for a design failure has been apportioned 60 per cent with a structural engineer at 40 per cent, reflecting the architect’s lead design role. In other cases a later professional’s intervening negligence has been so serious that it superseded the earlier breach, leaving the later professional with 100 per cent responsibility. Contributory negligence by the claimant — a client who ignored clear advice, or who withheld material information — will reduce the total recoverable and reshape the shares between the defendants.
Illustrative worked example, not a real case. A client instructs a solicitor to pursue a commercial dispute. The solicitor fails to identify a limitation issue at the outset. Counsel is then instructed to settle proceedings and also fails to catch the point. The claim is struck out. The client’s loss is £500,000.
The court considers each defendant’s role. The solicitor made the foundational error: identifying limitation was squarely within the retainer and should have been dealt with before instructing counsel. Counsel’s failure was secondary but not trivial — a competent barrister settling proceedings should have spotted the limitation issue and raised it. On the facts the court apportions 70 per cent to the solicitor (£350,000) and 30 per cent to counsel (£150,000).
In practice, the solicitor’s PI insurer typically pays the full £500,000 to the claimant and then pursues counsel’s PI insurer for the £150,000 contribution under the 1978 Act. That inter-insurer recovery is where much of the apportionment argument actually happens.
Professional indemnity insurers reserve claims and negotiate settlements against an anticipated apportionment. A defendant who expects to be found 20 per cent responsible will fight harder against a 50 per cent settlement demand than one who accepts 80 per cent exposure. Early expert input on the likely apportionment shapes the reserve, the negotiating posture, and whether Part 20 contribution proceedings are commenced. Where several insurers are on risk, a mediated split is often reached before trial to save costs — but the shape of that split is driven by how the two limbs above are likely to be weighed.
Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority. Firm reference number 724952. This entry is general information, not advice on any particular policy.