Why marketing agencies agency reviews need independent evidence

Reviews of marketing agencies are only as good as the evidence behind them. This guide explains why agency reviews need independent proof, and names the sources a buyer in the United Kingdom can check: filed accounts at Companies House, published award winners, media measurement data and regulator rulings.

What to take away

What was assessed

This review looks at how marketing agencies agency reviews are built, not at how any named agency performs.

The assessed parts are the criteria used to score an agency and the provenance of the evidence behind each claim. The review must also state a method and a date.

The weighting of those criteria matters as much as the criteria themselves. Set the weights before you score anyone, and write them down. Criteria a reader can copy include strategic thinking, creative quality, measurement and reporting, commercial results, client retention and team continuity. Score each on a labelled band, such as "no evidence", "vendor claim only", "documented" or "independently verified", rather than on a bare number.

What was not assessed: pitch performance, account team chemistry, day-to-day delivery, or any agency's current client work. Those need your own meetings and references. Editorial judgement here covers the review method only.

Vendor claims and independent evidence

A vendor claim is anything the agency says about itself: awards entered, growth figures, client logos, testimonials it selected. These may be true, but they are self-reported and unaudited.

Independent evidence comes from someone with no commercial interest in the sale, and it can be checked.

Here is a worked example. The sentence "We are the leading agency for retail brands" is a vendor claim unless a named client or award list confirms it. The sentence "A named client agreed to be a referee for this campaign" is independent evidence, because the client can be asked about the work.

When you read a review, ask which of the two each sentence rests on. If the answer is not clear, the review is doing marketing rather than assessment.

The checks that matter

Start with the review's own method. Look for named criteria, a scoring scale and a date. A review without a date is unusable, because agency teams, ownership and pricing all change.

Then check the finance and structure behind the agency. The British Business Bank publishes support and funding information for smaller firms, which is relevant when an agency claims rapid investment or growth.

The IPA Effectiveness Awards winners for 2020 list is published at https://ipa.co.uk/awards-events/effectiveness-awardsv1/winners-2020/, and the IPA publishes its effectiveness case studies from those awards. Where advertising claims are involved, check regulatory conduct. The ASA sets out its sanctions for non-compliance, including ad alerts and withdrawal of trading privileges, so a pattern of upheld rulings is a genuine signal.

Other sources are worth knowing by name. Companies House holds the accounts and filings an agency must submit, so its registered size and financial history can be checked rather than taken on trust. The Competition and Markets Authority enforces consumer protection law on misleading commercial claims, which is the route beyond the ASA when a claim misleads buyers.

Award claims are checkable too: the IPA Effectiveness Awards and the Effie Awards publish their winners, and a claim that cannot be traced to such a list is a vendor claim. For campaign results, the measurement bodies do the counting: BARB for television audiences, RAJAR for radio and ABC for media circulation.

Checklist before you trust a review

Where reviews fit your shortlist

A review narrows the field. It should never close it. Use reviews to build a shortlist, then verify with reference calls, a written brief and a paid discovery stage.

If your search is regional, location and sector coverage change what a shortlist should contain. An agency built around London consumer brand work is rarely the right fit for a regional B2B brief.

Neither replaces your own diligence.

Common questions

Are agency reviews independent?

Sometimes, but not always. Directory listings and sponsored placements are commercial products. Independent reviews name their criteria and disclose conflicts.

What should a review never claim?

It should not claim hands-on testing, interviews or client results it did not carry out. It should also avoid undated statistics.

How do I verify an agency's own claims?

Ask for award entry details, audited accounts, named referees and the dates of the work. Then check public sources: the IPA case studies, filed accounts at Companies House, or regulator rulings from the ASA and the Competition and Markets Authority.

Does a low score mean an agency is poor?

Not necessarily. Criteria differ by buyer, so a low score on consumer brand work may sit alongside a strong score on B2B demand generation.