Lakshmi Mittal, head of the world's largest steel group, has set the clock ticking on his hostile bid for French rival Arcelor after taking the $23.6bn (€18.4bn) offer directly to the group's shareholders.

Mittal, who announced his intention to launch the cash and shares bid five months ago, said this afternoon that the offer from Mittal Steel had opened and would last 30 business days before closing on June 29. His battle for control of Arcelor, which has been rejected by the company's board, has drawn in a record number of investment banks.