Chemicals giant Ineos and its founder, prominent Brexiteer Sir Jim Ratcliffe, have backed Theresa May’s EU withdrawal agreement.

Sir Jim, who said earlier this year that he planned to move to Monaco, announced on Wednesday that the “pragmatic and sensible” Brexit deal had his full support.

The firm that made him into the UK's richest person with an estimated £21bn fortune said in a statement that it had "consistently" supported reaching a deal which allowed frictionless trade and for the UK to reach its own trade agreements.

Sir Jim, came out in support of the leave vote before June 2016’s EU referendum. “The Brits are perfectly capable of managing the Brits and don’t need Brussels telling them how to manage things,” he said in 2015.

On Wednesday the recently knighted businessman clarified his position, stating: “I have made no secret of the fact that whilst I have long supported the concept of a common market within Europe I have never felt comfortable with the concept of ever closer union.

“A Brexit deal that moves us closer to an open European market has my full support.”

However, the withdrawal agreement faces being voted down in a crucial House of Commons vote next month with opposition coming from hard-line Brexiteers, moderates and remainers.

Former defence secretary Sir Michael Fallon said on Tuesday that he feared the deal was the “worst of both worlds”.

As political divisions have deepened, the business community has largely united around the position that any deal is better than none at all.

With the March deadline now less than four months away, urgency is growing for firms that face unprecedented upheaval if the UK crashes out of the EU.

Ineos, the UK’s largest privately owned company, said it foresees “significant risk" to its business, "partly from the risk of WTO level tariffs but primarily from the uncertainty of non-tariff barriers to trade with potential delays at ports disrupting complex supply chains”.

These risks have consistently been highlighted since before the referendum by figures pushing for the UK to remain in the EU.

Sir Jim owns the majority of Ineos which makes the raw materials for a broad range of essential products, including medicines, textiles, car parts and mobile phones.

As with many of the industries it supplies, Ineos relies on complex, international supply chains crossing multiple borders and faces a taking a hit from Brexit. In June Ineos announced ambitious European expansion plans.

The company has attracted criticism in the past, notably when its founder and chairman decided to move its headquarters to Switzerland in 2010.

It has also successfully pressured unions representing workers at its Grangemouth refinery to accept terms banning them from taking strike action for three years.