The Marine Stewardship Council (MSC), which operates a “blue tick” scheme to indicate the sustainability of fish, has been accused of creating an “illusion” of ethical sourcing, after a study reported that widespread labour abuses have taken place on the fishing vessels it approves.

One in five vessels where the crew reported abuses to the International Transport Workers’ Federation (ITF) over the last five years took place on ships catching seafood certified as sustainable by the MSC, researchers found.

Ten of these cases involved allegations of serious crimes, according to the study. These include forced labour, human trafficking and forced criminalisation.

In all, researchers identified 80 cases of labour abuses onboard 72 vessels in 25 MSC-certified fisheries across the globe, from North Sea haddock fisheries in Scotland to tuna fisheries in the Pacific islands.

The most common abuses reported were of unpaid or delayed wages, but also included excessive hours, violence, harassment or threats, denial of medical care and debt bondage.

The ITF, which commissioned the study, said the abuses reported onboard “blue tick” vessels were likely to be an underestimate as the researchers used only ITF data on 354 vessels. National unions, seafaring organisations and other maritime authorities also regularly received reports of abuses.

The MSC has long said it is an environmental organisation, with no social assurance mandate nor labour assessment capacity.

However, Chris Williams, ITF fisheries co-ordinator, said: “That risks masking abuses and leading people to buy products that aren’t necessarily what they think they are.”

Each ITF case, of which there were 462 in all, refers to reported labour abuses on a single vessel, but could involve multiple abuses. In one vessel, for instance, all 26 crew were said to have been owed wages, but this was recorded as a single case.

The study also identified repeat offenders; for instance, one North Sea fishing vessel had three alleged cases of withheld wages and one of debt bondage over a five-year period, while approved to sell its catches under the blue tick label.

Dr Jessica Sparks, co-author of the report, Slipping through the net: labour abuses in MSC-certified fisheries, said the analysis added to growing concerns that MSC’s policies and practices may obscure labour abuses in seafood supply chains by undermining enforcement efforts and reducing scrutiny.

The MSC has engaged in evolving efforts to support the elimination of forced and child labour in supply chains. For instance, it has identified itself as a good “ally” to those fisheries seeking to show progress on labour standards and “prohibits” any of those that have been successfully prosecuted for forced or child labour.

Sparks said the problem with the policy of excluding any vessels with convictions for forced or child labour is that there were very few prosecutions. It also, she said, focused on a narrow legal definition, overlooking – and potentially minimising – a host of other exploitative practices and harms.

She added that in 13 years of working in the area, she could think of only one or two cases of prosecutions for human trafficking into forced labour. “The MSC says ‘we don’t certify for social’, yet they have these pre-eligible conditions for certification,” she said.

This led to an “illusion” of ethical sourcing, without providing mechanisms to identify or remedy abuses, Sparks said.

The International Labour Organization estimated in 2022 that about 128,000 workers were trapped in forced labour on fishing vessels globally.

For the report, researchers used a dataset of 462 cases of abuse recorded by 15 trained ITF inspectors on 354 unique vessels across the globe and cross-referenced these with a database of MSC-certified fishing vessels created from MSC’s Track a Fishery website and other publicly available information.

A spokesperson for the MSC said: “We agree that MSC’s policies are no substitute for businesses’ human rights due-diligence responsibilities and we make no claim to offer social assurance.”

MSC said that addressing forced and child labour issues in the seafood sector was a significant challenge requiring “industry-wide” collaboration.

Regarding pre-entry requirements banning any fisheries with convictions for forced or child labour, the spokesperson said: “As an environmental organisation without a social assurance mandate or labour assessment capacity, convictions provide a clear, objective and legally robust basis for confirming forced labour.”

The spokesperson added that MSC had ended the use of third-party social audits after an expert panel found they were ineffective on labour issues. The not-for-profit organisation is creating a third-party online information portal, as recommended by the expert panel, to support transparency.