The world’s largest drilling company Boart Longyear has had its credit rating downgraded as it braces for a tough year ahead.

Ratings agency Standard and Poor’s cut the company’s credit rating from B+ to B, and revised its ratings outlook from stable to negative.

Boart recently recorded a loss of $US329 million ($A366.13 million) for the first half of 2013, driven largely by massive falls in earnings in its drilling services division as mining companies continue to slash their exploration budgets.

Around half the company’s drilling rigs are now laying idle and it has slashed 2,800 staff this year.

Shares in the company were down one cent at 48.5 cents at 1230 AEST.