Employment lawyers throughout the UK are watching keenly as retail giant Sports Direct tackles a multi-million pound legal dispute from workers.

The company’s 2013 decision to exclude employees operating on “zero-hours” contracts from a £160m bonus scheme is being challenged by employment law solicitors acting on behalf of nearly 300 staff.

The legal tussle could help clear up question marks over the employment status of the rest of the country’s zero-hours workers, who make up about 4% of the total workforce.

Employment solicitors say there’s no legal definition of a zero-hours worker, meaning their employment rights exist in a legal grey area.

Sports Direct has already been made to spell out the limited employment terms under its zero-hours contracts after a case brought by an ex-employee last year.

The retailer agreed to specify in job adverts and add information to contracts and staff rest areas stating precisely what employees can expect under the terms of their contract.

Almost one in ten Sports Direct workers are employed on zero-hours contracts.