The US President Donald Trump has once again insisted that he was not involved in the decision of his Vice President Mike Pence to stay at the Trump International Golf Links and Hotel in Doonbeg, Co Clare.

Mr Pence spent two nights at the property last week during his visit to Ireland.

Speaking to reporters at the White House this evening, Mr Trump referred to Mike Pence's family links to Doonbeg and the fact that the US Vice President had previously stayed at the hotel years ago, before it was owned by the Trump Organisation.

"He told me that he stayed there many years ago, before I bought it," Mr Trump said.

He said he had nothing to do with Mr Pence's decision to stay at Trump Doonbeg but added that his Vice President "has good taste".

On Friday, Democrats in the US House of Representatives announced that they had launched an investigation into the decision by Mr Pence to stay at the Doonbeg hotel

Democrats have accused the Vice President of funnelling US taxpayers' money into a Trump business and have requested documents from the White House, the office of the Vice President, the Secret Service and the Trump Organisation.

The committee wants to establish how the decision was made, how much the stay at Trump Doonbeg cost and if it was a violation of the US constitution's emoluments clauses.

The US House Oversight Committee and the US House Judiciary Committee have sent a series of letters requesting information on what they described as "multiple efforts by the President, Vice President, and other Trump Administration officials to spend taxpayer funds at properties owned by the President in potential violation of the constitution’s emoluments clauses".

Last week, Mike Pence's Chief of Staff Marc Short said that Donald Trump had suggested staying at the hotel but the US president said this was not the case.

"I had no involvement, other than it's a great place," Mr Trump told reporters on Wednesday.

Separately, Mr Trump today denied any knowledge of members of the US Air Force staying at one of his resorts in Scotland.

The Air Force has ordered of a review of its guidelines for overnight accommodation after it emerged that some members had been staying at Trump Turnberry. 

The Democratic-led House Oversight Committee is seeking information about the US Defence Department’s ties to the Trump golf resort and the nearby Glasgow Prestwick Airport.

Today Donald Trump tweeted that he was not involved.

"I know nothing about an Air Force plane landing at an airport (which I do not own and have nothing to do with) near Turnberry Resort (which I do own) in Scotland, and filling up with fuel, with the crew staying overnight at Turnberry (they have good taste!). NOTHING TO DO WITH ME" he wrote. 

Speaking at the White House this evening, Mr Trump told reporters that he would be releasing a financial report before next year's election and that people would be "extremely shocked" at the scale of his holdings.

"I don't need to have somebody take a room overnight at a hotel," he said.

US House steps up Trump impeachment probe

Meanwhile, Democrats have moved to intensify their impeachment investigation of President Donald Trump as whiffs of new scandal surrounding the White House emerged related to Mr Trump's business and his lawyer's involvement in Ukraine.

While the Democrat leadership remains reluctant to go all-in on impeachment, given that the Republican-controlled Senate would vote down any effort to oust Donald Trump, the stepped-up investigation could add further pressure on the embattled president 14 months before the next elections.

House Judiciary Committee Chairman Jerry Nadler moved to formalise an investigation that had up to now avoided officially declaring the aim to impeach President Trump and put him on trial in the Senate.

He laid out new procedures that he said would govern "the committee's investigation to determine whether to recommend articles of impeachment with respect to President Donald J. Trump."

He also defined the investigation along four specific lines: allegations that Trump illegally interfered with the Russia election meddling investigation, that he took part in hush payments to alleged former mistresses, that he has used his office to enrich himself, and that he offered pardons to government and campaign officials to protect him.

"No one is above the law," Mr Nadler said in a statement.

"The unprecedented corruption, coverup, and crimes by the president are under investigation by the committee as we determine whether to recommend articles of impeachment or other Article 1 remedies," he said, referring to the US Constitution's section on legislative powers.

House Speaker Nancy Pelosi remains opposed to efforts aimed at Mr Trump's impeachment

In recent weeks more than half of the 235 Democrats in the House of Representatives have endorsed impeachment, even as senior party officials, especially House Speaker Nancy Pelosi, continue to resist it.

Ms Pelosi has made clear she believes the party needs to focus its energies on defeating Donald Trump and the Republicans in the November 2020 election.

Mr Nadler's new rules, which are expected to be passed by the committee on Thursday, will govern how witnesses will be called and questioned and how Mr Trump's lawyers will be involved.

They are also expected to provide the committee with a broader ability to subpoena witnesses and documents, in the face of resistance by the White House.

"We will not allow Trump's continued obstruction to stop us from delivering the truth to the American people," Mr Nadler said.

Meanwhile the Democratic heads of three other House committees announced an investigation into alleged efforts by President Trump and his lawyer Rudy Giuliani to pressure the Ukrainian government for their own political ends, including by withholding US security assistance.

They allege that Trump and Giuliani have pressured Kiev to prosecute Ukrainians who provided evidence against Donald Trump's former campaign manager Paul Manafort in the Russia meddling investigation.

They also alleged that Kiev was pressured to provide damaging information on the son of former Democratic vice president Joe Biden, who could face Mr Trump in next year's presidential election.

Hunter Biden worked for a Ukrainian gas company beginning in 2014, while his father was vice president.

Additional Reporting AFP