A Republican congressman has been accused of spending $600 of his campaign funds to fly his family's pet rabbit around the US.

A review of Representative Duncan Hunter's campaign finances by the House of Representatives Committee on Ethics is said to show "in cabin rabbit transport fees," according to Hunter's spokesman Joe Kasper, who spoke about the charges for the family pet.

"(The office) has in their report $600 in campaign expenditures for in cabin rabbit transport fees," Kasper told the Press-Enterprise newspaper. "Since travel is often done on (airline) miles – which is entirely permissible — the credit card connected to the account was charged several times even when his children were flying."

Hunter, who represents California's 50th congressional district, has been investigated by the House Ethics Committee over the past year. A report on his campaign finances was supposed to be released by the group, but has been delayed by the swearing in of the new Congress.

The Committee came under attack this week at the beginning of the 115th Congress when House Republicans attempted to restructure it and reduce its power. But they abruptly reversed their attempts after the move was criticised by President-elect Donald Trump. On Twitter Trump wondered why "weakening" the Independent Ethics Watchdog was "their number one act and priority?"

Hunter's spokesman said that the ethics office report's "findings or implications are significantly misrepresented or even exaggerated" and cited the costs for the pet rabbit as an example.

In the past year Representative Hunter has given $62,000 back to his campaign after the ethics committee found that campaign money had been spent on oral surgery, a garage door, video games, resort stays and jewelry bought in Italy.

Under campaign finance law, candidates cannot use the money for personal benefit because it might give influence to donors. Hunter has given back $6,000 in campaign funds used on United Airlines.

"Many of Rep Hunter's repayments had to do with mistakes under specific circumstances, and in other cases there were bona fide campaign activities connected to expenditures that [the office] was not aware of and didn't account for," Kasper told the Press-Enterprise.

"This was nothing more than an oversight," he said. "In fact, it's such an obvious example of a mistake being made but (the office) wants to view it through a lens of possible intent."