Belgium’s Saverys family has increased its Euronav stake again a day before a crucial board vote that could determine whether the tanker company merges with John Fredriksen’s Frontline.

The clan’s shipowning company CMB and holding company Saverco now have 37.28m shares or 18.5%, extending the lead as the biggest shareholder.

This is up from 17.5% earlier in May.

Between 12 and 17 May, CMB acquired another 2.03m shares at $10.93 each for an outlay of $22.2m.

The holding is now worth $410m.

The Saverys family is opposing the Frontline merger and wants to combine the company with its hydrogen and ammonia shipping company CMB.Tech instead.

CMB is proposing three new directors at an annual general meeting of shareholders on Thursday to seize control of the supervisory board. Euronav is proposing one new independent director, investment banker Steven Smith.

Euronav’s management is backing the deal with Fredriksen to create the world’s largest crude tanker company with a market cap above $4bn.

CMB’s increasing shareholding could be crucial in the future.

If Euronav carries the day at the shareholders’ meeting, a vote will then take place at a later date to approve the merger deal.

If this is structured as a straightforward combination then bosses will need a 75% majority of the votes.

But other structures will need a lower hurdle, including an acquisition requiring a simple 50% plus one vote.

Fredriksen’s Famatown Finance is the second biggest Euronav shareholder at about 12%.

Under the proposed all-share deal, Euronav would own 59% of a combined entity, and Frontline 41%.