Republican congressman is filmed screeching 'You f**k with my family, I'll end every relationship you have' in foul-mouthed rant at DC holiday party

A Republican congressman representing upstate New York was caught on camera at a holiday party in Washington DC on Thursday night threatening a stunned-looking former staffer.

Brandon Williams, 56, jabbed his finger towards Michael Gordon in the hearted confrontation at the International Spy Museum, during a festive gathering hosted by a lobbying company.

Williams yells at Gordon: 'You f*** with my family, I'll end every relationship you have.'

Gordon, looking taken aback, tells Williams: 'I didn't do anything.'

Williams presses closer to Gordon, squaring up to him and still yelling.

'Do you understand me? You think I don't know?'

A woman interrupts, and says: 'Excuse me? Hello?'

Williams, realizing the intensity of the confrontation, steps back, and pushes aside a camera filming the encounter.

'Hey, why don't you get the police in?' he asks as he storms away.

A spokesman for Williams later said that the row was sparked by the behavior of Gordon and another former colleague, Ryan Sweeney.

Gordon and Sweeney were sacked for disparaging female members of Williams' family, the spokesman said.

'What you are seeing is two former staffers who were fired by the Congressman earlier this year,' the spokesman said.

'Both individuals, the one being confronted by the Congressman and the one filming, made rude comments about the female members of the Congressman's family.

'These individuals planted stories with the media and one of them physically shoved the Congressman at a holiday event (edited from the video).

'As a former nuclear submarine officer known for his temperament and poise, tonight should be a lesson to all, never go after this Navy Nuke's family,' the statement concluded.

Neither Williams nor Gordon have commented on the encounter.