A formal sexual harassment complaint has been made against Barnaby Joyce, the Nationals have confirmed.
"The Federal Party can confirm a formal complaint has been received," Nationals Federal Director Ben Hindmarsh said in a statement.
"All complaints are taken seriously and treated with strict confidentiality and given due process."
A spokesman for Mr Joyce told News Corp he had been made "indirectly aware" of the claim which he described as "spurious and defamatory".
"He said allegations of wrongdoing should be immediately referred to police so that the veracity of any claim could be properly tested," the spokesman said.
Earlier on Thursday, Victorian Nationals MP Andrew Broad became the party's first federal representative to call for Mr Joyce to resign.
Mr Broad will move a resolution at Monday's party room meeting asking his leader to go to the backbench on the advice of his branch members.
