AT first it seemed like just another piece of jokey excess on the part of President Donald Trump, but now the scandal over whether he asked his friend Ambassador Woody Johnson to try to persuade the UK Government to get the Open Championship back to his Turnberry course has taken a very serious turn.

The two Democrats in the House of Congress who called on Ambassador Johnson to resign after the scandal started have now asked that the Federal Bureau of Investigation (FBI) inquire into whether Johnson committed an illegal act. That inquiry could involve the man who was allegedly asked by Johnson to try to get The Open for Turnberry, former secretary of state for Scotland David Mundell MP.

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Under the American constitution, no sitting president can use his office to make gains for himself or his family.

Representatives Ted Lieu and Kathleen Rice called on the FBI to investigate allegations Johnson “abused his position and tried to steer the lucrative British Open to the Trump Turnberry Resort”.

In a letter to FBI director Christopher Wray, the two politicians requested that the FBI evaluate whether “Ambassador Johnson solicited bribes by offering to take official acts in exchange for moving the British Open to a property owned by the Trump family”.

They added: “We don’t know the details of Ambassador Johnson’s conversations with British officials, but if he was being influenced in the performance or omission of any official acts in exchange for foreign officials to move the British Open to Trump Turnberry, that would constitute solicitation of a bribe.”

They argued that under American law, it is a felony if a “public official” directly or indirectly “seeks, receives, accepts or agrees to receive or accept anything of value personally or for any other person or entity, in return for being influenced in the performance of any official act” or “being induced to do or omit to do any act in violation of the official duty of such official or person”.

The two added: “In this case, Ambassador Johnson is a public official and he sought something of significant value – moving the British Open to Trump Turnberry – for Donald Trump. If Ambassador Johnson’s conversations with British officials included him stating he would perform or omit to perform certain official actions in exchange for moving the British Open, then all the elements for soliciting a bribe are met.

“We believe the public reporting has provided more than enough of a factual predicate to open an investigation into Ambassador Johnson.”

In his first broadcast interview since the story was published in the New York Times last month, the man who made the original allegations, former diplomat and Johnson’s deputy in London, Lewis A Lukens, told Rachel Maddow of MSNBC that the Ambassador did meet with David Mundell. Lukens said: “The Ambassador came back from a meeting at the White House. The very next morning he came and talked to me and said ‘the president wants me to do this. Who should I talk to, how should I go about doing it?’

“I said you can’t, you shouldn’t do it, it’s unethical and probably illegal. A couple of weeks later he asked again and I gave him the same answer, and then he went and had a meeting with the British minister responsible for Scotland and made the request, made the suggestion at least.”

Trump has denied ever asking Johnson to get the Open to Turnberry, and the UK Government says no such request was made. When the story originally surfaced, the R &A who own the Open said: “We haven’t received any approaches from the British Government or the Scottish Government about this.” The National asked David Mundell if he would co-operate with an FBI inquiry but no reply had been received by the time we went to press. Any reply will be posted on our website.