The prime minister also insisted that the UK would prosper outside the EU with or without a trade deal, a source on the phone call with industry told HuffPost UK.
But Johnson stressed that, while companies have been “terribly busy with Covid”, they must now get on and prepare for the end of the Brexit transition on December 31.
Michael Gove, who appeared alongside Johnson on the 21-minute call, meanwhile tried to reassure those present by saying Brexit was like moving house – initially expensive but with long-term benefits.
The Tuesday afternoon call came after the PM on Friday said the UK must prepare for the transition to end without a Brexit trade deal, and with a default to World Trade Organisation terms for trading with the EU – widely predicted to be the most economically damaging outcome.
One industry source said the mood among leaders on the call was “disappointment” as they wanted “a bit more certainty on how it would play out if we are to leave without a deal”.
They wanted to see that Johnson and Gove understood the difficulties and specifics of what was being planned and “some sense of the needs of businesses”, the source said.
And they also bemoaned the fact that the questions seemed pre-selected as there was no mechanism for industry leaders to jump in with a query.
Gove did seem open to demands led by the CBI lobbying group for a business taskforce to help companies prepare.
And he promised to look at the introduction of “transition vouchers” – cash payments to help firms prepare for the potentially huge change in trading terms from January 1, the source said.
Ireland has operated a similar scheme, giving firms 9,000-euro grants to help them get ready for new trading terms with the UK.
The call came as the UK chief negotiator Lord David Frost held more talks with his EU counterpart Michel Barnier.
🇪🇺🇬🇧 I spoke again to @DavidGHFrost today. My message: we should be making the most out of the little time left.
Our door remains open.
— Michel Barnier (@MichelBarnier) October 20, 2020
On Monday, Barnier attempted to unblock the stalled negotiations by offering for the first time to work on the legal text for an outline Brexit trade deal.
But Frost rebuffed his offer and demanded that the EU makes a “fundamental change in approach to the talks and make clear it has done so”.
Following another call with Frost on Tuesday, Barnier said: “My message: we should be making the most out of the little time left.
“Our door remains open.”
A Downing Street spokesperson responded: “Lord Frost and Michel Barnier had a constructive discussion.
“The situation remained as yesterday, and they will remain in contact.”
No.10 sources meanwhile refused to comment on the specifics of the call Johnson and Gove had with business leaders, describing it as a “private” event.
Downing Street later provided limited quotes of the call.
Johnson told business leaders: “Our job is to create the platform for dynamic businesses such as yours to compete and to grow.
“But it is vital that everybody on this call takes seriously the need to get ready, because whatever happens – whether it’s Canada or Australia – change is going to happen.
“There is a big opportunity for this country and we want to help all of you to seize that opportunity.”
Gove said: “I am hugely appreciative of the efforts that so many companies have made over the course of this year, both to help us deal with the Covid crisis and also to prepare for the end of the transition period.
“We know that this December 31 we will be leaving the customs union and single market come what may.
“It’s in law, and it’s a fact that the EU and UK accept as immoveable, and that means we need to make sure we’re ready.”
This article originally appeared on HuffPost UK and has been updated.