Protecting Donald Trump’s family is putting a major strain on Secret Service agents, a senator from the US leader’s Republican Party has claimed.

“They are flat worn out,” Jason Chaffetz told The New York Times, adding that more staff were needed to keep up with the demands.

The agency has seen staff levels drop to approximately 250 agents and 350 administrative and technical staff, but it currently has around 40 per cent more people under its protection than in previous non-campaign years.

Mr Trump’s wife Melania and son Barron are currently living in New York’s Trump Tower and agents have also been required to guard his four adult children and their families.

The US leader has also requested protection detail for aides like Reince Priebus and Kellyanne Conway.

As a result, dozens of agents have been temporarily pulled off criminal investigations to serve two-week stints protecting members of the first family.

Dan Bongino, a former Secret Service agent and author of The Fight: A Secret Service Agent’s Inside Account of Security Failings and the Political Machine, told The Independent that as a result, the agency is “on the verge of catastrophic collapse based on attrition rates”. In speaking to former colleagues he said resignations occur “almost daily”.

He added that there would be less strain on resources if law enforcement agencies did not conduct parallel, duplicate investigations. It would free up the Secret Service to focus on unique cases as well as protection duties.

But he said that more money in the $1.9bn (£1.5bn) budget is not the only answer according to Mr Bongino, who pointed out that under George W Bush’s administration, the budget was far less.

But he said their duties needed to be reorganised.

“The majority of the criminal mission needs to go,” he said.

Though the House Oversight and Government Reform Committee is discussing the matter, Mr Bongino said he was “not optimistic” they will make the necessary reforms.