Donald Trump changed his tune on Mexico’s richest man after meeting him at Mar-a-Lago, but perhaps more surprising was the revelation that Carlos Slim may have arranged to meet the president-elect through a private lobby group.

Mr Trump met telecoms billionaire Carlos Slim last weekend for dinner at his Florida resort, even though the two businessmen had recently accused each other of being racist and leading a media conspiracy.

Ben Carson’s former campaign manager, Barry Bennett, told Politico that his new lobbying firm partner, Mr Lewandowski, had travelled to Mexico City this month to meet with Mr Slim and had arranged the meeting.

The revelation could undermine Mr Trump’s message that he wants to "drain the swamp" in Washington DC of rich, powerful lobbyists.

The meeting, which happened just 10 days after Mr Lewandowski met Mr Slim, also casts a shadow over potential conflicts of interest between government business and a private lobbying group.

Lobbying firm Avenue Strategies' website advertises the Me Lewandowski and Mr Bennett's close relationship with Mr Trump and the proximity of their office to the White House. Their office building also houses the Trump transition team.

Mr Bennett told Politico that Mr Slim might become a client of their firm, Avenue Strategies, next year.

"It's unknown," he said. "Everyone would love to have Carlos Slim as a client."

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Mr Lewandowski flatly denied that any money had changed hands.

He responded that he travelled as a private citizen to Mexico City and was not "paid a dime" or given a contract. He said there was "no factual basis" for him trying to recruit Mr Slim as a client.

Mr Trump’s spokeswoman, Hope Hicks, also denied that the president-elect was being sold for access.

Whether money is exchanged or not, the Justice Department's Foreign Agents Registration Act requires anyone acting as a representative to foreign individuals or foreign governments report their political activities within 10 days of "agreeing to become an agent and before performing any activities for the foreign principal".

Mr Trump previously accused Mr Slim, who is a major owner of shares in the New York Times, of leading a media conspiracy to defeat him during the campaign.

"The New York Times strings are being pulled by Mexico's Carlos Slim, a billionaire who benefits from NAFTA and supports Hillary Clinton's open border policies," he said in a statement in October.

Mr Slim also scrapped a television deal in June 2015 with Mr Trump after accusing he accused the president-elect of racism.

But the president-elect appeared to have changed his tune after the meeting last weekend.

He tweeted: "Yes, it is true — Carlos Slim, the great businessman from Mexico, called me about getting together for a meeting. We met, HE IS A GREAT GUY!"

He told the Washington Post that he had "a lovely dinner with a wonderful man".