TESCO supermarket this week says it's working with the World Wildlife Fund to help protect the seas from overfishing.

According to research 94 per cent of all fish stocks are either overfished or at a maximum sustainable level, with Tuna among the most at risk.

The store says it will work with suppliers to "introduce new due diligence processes within its tuna supply chain" and support fishery improvement projects.

It also says it's encouraging an industry-wide adoption of a metric to report on the health of fish stocks - this will allow Tesco and its suppliers to know if their fish is being sourced from a sustainable marine environment.