Health Secretary Jeremy Hunt has said that “threats” by business over Brexit are “completely inappropriate”.
He was responding to warnings by Airbus and BMW that investments in the UK could be jeopardised by Brexit uncertainty.
Speaking on The Andrew Marr Show, Mr Hunt said Brexit discussions were at “critical moment” and needed unity.
Last week, Airbus warned it could leave if the UK exits the single market and customs union with no transition deal.
BMW followed the warning from Airbus by saying that clarity over Brexit is needed by the end of the summer.
In response Mr Hunt said: “It’s completely inappropriate for businesses to be making these kinds of threats.
“We are in an absolutely critical moment in the Brexit discussions and what that means is that we need to get behind Theresa May to deliver the best possible Brexit.”
BMW makes the Mini and Rolls Royce and employs about 8,000 people in the UK.
BMW UK boss Ian Robertson said he needed to know within months what the government’s preferred position was on customs and trade post Brexit.
“If we don’t get clarity in the next couple of months we have to start making those contingency plans… which means making the UK less competitive than it is in a very competitive world right now,” he said.
“That is a decisive issue that ultimately could damage this industry.”
BMW has built up an alternative manufacturing base in the Netherlands amid concerns about Britain’s suitability as an export hub after Brexit.
The customs union brings together the EU’s 28 members in a duty-free area, in which they pay the same rate of duty on non-EU goods.
Prime Minister Theresa May has ruled out staying in the customs union after the UK leaves the EU on 29 March 2019.
Airbus, in its Brexit “risk assessment” published on Thursday, said if the UK left the EU next year without a deal – leaving both the single market and customs union immediately without any agreed transition – it would “lead to severe disruption and interruption of UK production”.
The European plane-maker said the warning was not part of “Project Fear”, but was a “dawning reality”.
The term “Project Fear” has been used by some pro-Brexit campaigners to denote alleged scaremongering by those in favour of remaining in the EU.
The former director-general of the British Chambers of Commerce, John Longworth, who co-chairs Leave Means Leave, said Airbus had given similar warnings years ago.
“They’ve also said that they’re quite prepared to move production to places like China, which is not even in the European Union,” he told the BBC.
“So how can that possibly be anything to do with Brexit?”
Airbus’s 14,000 UK staff are employed across 25 manufacturing sites. About half are in Wales.
The company, which makes wings for the A320, A330/A340, A350 and A380 passenger planes in the UK, also said the current planned transition period, due to end in December 2020, was too short for it to make changes to its supply chain.
As a result, it would “refrain from extending” its UK supplier base. It said it currently had more than 4,000 suppliers in the UK.
Between 2012 and 2015, BMW Group invested £750m to upgrade manufacturing sites in Oxford, Hams Hall and Swindon.
The company also has its Goodwood manufacturing plant in West Sussex, a UK sales and marketing subsidiary in Farnborough and a vehicle distribution centre in Thorne.