A review is under way of legislation which makes it legal to pay foreign sailors working in the North Sea less than the minimum wage.

At times more than half of the foreign-flagged vessels used by the oil and gas industry employ crew on less £6.70 an hour, according to the International Transport Workers' Federation (ITF).

Transport minister John Hayes pledged to re-examine the legislation last month after questions were raised in parliament about the treatment of overseas workers.

The UK's Department for Transport is expected to announce the findings of its review next year.

One Indian sailor serving aboard a vessel which has been detained twice in Scotland this year over crew pay said he believes all sailors should be paid equally.

"In India there are many new officers like me and just getting a job is enough for them, they're not concerned about salary," he said.

"But in the last six months I've seen the culture of the UK and I now agree that wherever we work we should be paid accordingly."

Foreign-flagged vessels are contracted to UK firms through shipbrokers in Britain, but it is legal to pay seafarers less than the minimum wage if they are recruited overseas.

A protest was held in Aberdeen last month over claims that sailors serving aboard Northern Isles ferries on a Scottish Government contract were being paid around £4 an hour.

Northlink, which sub-contracted the route between Aberdeen and Shetland to Seatruck, has offered to cover the cost of paying ferry workers the basic rate.

But Seatruck claims that offering the minimum wage would "distort its fleet-wide pay structure", leading the RMT Union to brand the ferry a "ship of shame".

Unions argue that extending the minimum wage legislation to everyone in the North Sea would improve conditions, create jobs in the UK, increase tax returns, and make the industry more competitive.

It has been suggested that it may be possible to expand the legislation without altering it as it is already possible for seafarers to apply for minimum wage protection on an individual basis if they can prove they "ordinarily" work in the UK.

Campaigners believe this could be extended to automatically include all foreign sailors who regularly serve in British waters.