First daughter Tiffany Trump's recent holiday to Berlin, Germany, cost the US taxpayer more than $22,000.

President Donald Trump's youngest daughter visited the German capital with her boyfriend last month for a 10-day holiday. Her trip abroad cost US taxpayers $22,439, according to purchase orders obtained by CBS News.

The total sum covered the hotel expenses of US Secret Service agents who accompanied Trump on the trip, but did not include the cost of the agents' flights.

"URGENT! Rooms Regent USSS (Tiffany Trump visit) June 14-24," one of the orders read, suggesting that the trip had been planned last minute.

It is common practice for secret service agents to vet a site on the itinerary of the president or one of his family before their arrival.

As the Secret Service does not have an office in Berlin, agents had to work from a "temporary office" in a hotel "control room."

After spending several days in Berlin, Trump travelled on to Budapest with boyfriend Ross Mechanic. She shared pictures on her Instagram account of the couple posing in front of the Brandenburg Gate in Berlin and standing on Heroes' Square in the Hungarian capital.

No purchase orders for the Budapest trip have yet been released.

The Trump family are seasoned travellers who are regularly photographed on luxurious holidays abroad. But since their father became president, the Trump children have faced increased scrutiny when travelling overseas.

In January, the president's son Eric racked up nearly $98,000 in expenses when he travelled to Uruguay for a business trip. When Trump's two eldest sons visited Vancouver in February for a hotel opening, secret service costs amounted to $15,000.

The Secret Service asked the Office of Management and Budget earlier this year for an extra $60 million to cover their costs accompanying the Trumps on foreign trips.

While many have criticised the trumped up expenses, others have argued that safety precautions to protect the Trump family are necessary.

"If Eric Trump is traveling and let's say, God forbid, gets attacked and hurt, killed—imagine the impact, the psychological impact, that would have on the president," Obama-era Secret Service agent Jonathan Wackrow told NPR at the time. "So by protecting the children, you're by default protecting the sanctity of the office of the presidency."