It is the first public campaign for his $600 million multistrategy fund, Sparta Capital, which said it has had six private meetings with the company, until the letter it published on Thursday. In the letter, Tuil said the Wood share price is cheap enough to make it the target of a takeover and believes that it has sufficient cash for a share buyback.

Wood did not immediately respond to request for comment.

Shares in Wood Group were last up 2.2% on Thursday. They've fallen this year by 33%, having hit two-year lows at one point.

(Reporting by Nell Mackenzie; Editing by Amanda Cooper)

By Nell Mackenzie