Philip Hammond and David Davis are to present a united front to businesses on Monday amid concerns that a cabinet split is emerging in the government’s approach to negotiating the UK’s exit from the European Union.

The chancellor and the Brexit secretary will attempt to reassure businesses that they have been working increasingly closely together. The joint event follows suggestions of a split over whether the government ought to be willing to pay significant sums of money in return for access to the European single market.

The foreign secretary, Boris Johnson, dismissed the idea as “pure speculation”, arguing that the UK must regain control of money sent to Brussels, and should not agree to more than small contributions.

His comments came just days after Davis said the government would not rule out the possibility of financial contributions to secure “the best possible access for goods and services”.

The Brexit secretary made the assertion to MPs in the House of Commons, and the idea was reinforced later by Hammond and by Downing Street.

Johnson – who was a leader in the Vote Leave campaign, which suggested Brexit would result in an extra £350m a week available to be spent on the NHS – tried to play down the idea on the BBC’s The Andrew Marr Show.

“That is obviously something that David Davis is considering but it doesn’t mean a decision has been taken … I am not going to get involved in the minutiae of our negotiating position before we trigger article 50,” he said.

He stressed that regardless of Davis’s claim he felt the country must “be able to take back control of the money that we currently give to Brussels” after Brexit.

He said the UK could pay in for some elements of “European cooperation” in future, such as the Erasmus student exchange programme.

But when Marr asked him whether that could include contributions for single market access, Johnson replied: “That is a pure – that is speculation.”

He added that any payments ought to be small. “My own view is I see no reason why those payments should be large and, as I say, I do see a big opportunity for us to take the money that we’re getting back and spend it on other priorities.”

Whitehall sources played down the idea of any divide, arguing that all ministers agreed that leaving the EU would stop automatic contributions into the EU budget. They argued that Johnson, as well as Hammond and Davis, remained open-minded on other issues.

However, the question of payment is more politically difficult for Johnson because of the £350m promise, while Davis has taken steps to make clear that he “made no such pledge” during the EU referendum.

Whitehall sources were reported in the Sunday Times as saying Hammond and Davis had formed a “small clique” in government. However, others denied that was the case.

One told the Guardian: “They have been working closely together for some time, reassuring businesses that they have heard their concerns and will work to ensure that they won’t lose out.” But they denied there was a wider split.

Johnson used a media round to also argue that while he wanted Britain to have control over immigration he believed that it was right to persuade voters that the desire of workers to come to Britain was a “massive compliment and tribute to the UK economy”.

He said Brexit gave the UK the chance to become the leading advocate for global free trade and that should be the government’s focus.

“There are pressures around the world, people who want to pull up the drawbridge and we have got to fight against them and that is the way to global growth,” he said, arguing that 330,000 net migration was “very high”, but not appearing to support government policy to reduce it to the tens of thousands.

The foreign secretary also told ITV that international students should be taken out of the immigration figures. He said people coming to study was a “massive benefit to this country”.

And he addressed controversy over the anonymous suggestion from four ambassadors that he had privately told them he supported free movement.

Asked about it by Dermot Murnaghan on Sky News, one of the organisations that broke the story, he replied: “With great respect I think your story was a dud, it was wrong, it was a load of old baloney.

“That is not your fault, not the journalist – he was offered something completely untrue.”

Other ambassadors who were at the event have since claimed that he did not say anything controversial, but simply set out his positive views about immigration before reiterating that control was required.

It all comes as Theresa May suggested ministers should not be thinking of the black and white demands of leave and remain hardliners, but instead try to achieve a “grey Brexit”.