Offshore oil and gas workers have secured a sector-leading pay rise of 8.6 per cent after threatening industrial action against a key labour hire firm.

The Offshore Alliance, a team-up of the Australian Workers Union and Maritime Union of Australia, revealed on Monday it had reached an in-principle deal with Rigforce that guarantees about 60 drill workers a 15.6 per cent pay rise over two years, made up of 8.6 per cent this year and 7 per cent next year.