Limousine services used over the course of Mike Pence's official state visit to Ireland cost US taxpayers close to $600,000 (€545,000).
The US Vice-President stayed at Trump International Doonbeg in Co Clare for two nights last week, despite his official meetings taking place in Dublin.
US State department receipts show more than $599,000 was paid to JP Ward and Sons - a limousine company based in Co Wicklow.
The same company had received almost $1 million during Donald Trump's visit earlier this year.
According to US government data, the costs cover 'transportation, travel, lodging and recruitment' related limo services.
Highlighting the limousine costs, the Citizens for Responsibility and Ethics in Washington (CREW) group said Mr Pence's stay in Doonbeg was 'highly inconvenient and extremely expensive'.
They said: "Pence’s $600k limo bill does not even cover the full cost of the trip, because it excludes the cost of Secret Service detail and lodging.
"CREW sent a Freedom of Information Act request for Secret Service records for a more complete picture of what the detour cost taxpayers."
Last week it emerged that the US House of Representatives has already launched an investigation into the decision for Mr Pence to stay in Doonbeg - a decision which US President Donald Trump has denied any involvement in.
I had nothing to do with the decision of our great @VP Mike Pence to stay overnight at one of the Trump owned resorts in Doonbeg, Ireland. Mike’s family has lived in Doonbeg for many years, and he thought that during his very busy European visit, he would stop and see his family!
— Donald J. Trump (@realDonaldTrump) September 9, 2019
The US House Committee on Oversight and Reform has sent a series of letters requesting documents and information regarding administration spending at properties owned by President Trump.
The committee claims this could be in violation of emoluments clauses in the US constitution.
Chairman of the committee, Elijah E Cummings, said: "The committee does not believe that US taxpayer funds should be used to personally enrich President Trump, his family, and his companies."