A US state senator from New Hampshire has been arrested after he allegedly slapped and spit on an employee at an Irish bar during an argument. 

Murphy, a Republican state senator from Manchester, New Hampshire, was charged with two counts of simple assault and one count of criminal threatening. 

The alleged incident took place in April at Murphy's Taproom, which Murphy owns, according to Manchester police. 

Murphy turned himself in last Monday to face the charges and said on Tuesday that he is innocent and looking forward to his day in court. 

"When the facts are known it will be clear that the police have charged the victim in this case," Murphy said in a post on Facebook. 

"I will be defending my name, reputation, and business through the legal process." 

He has been released on personal recognizance bail and will be arraigned on July 24. 

The employee reportedly claimed that Murphy spat on him and slapped him during an argument at the bar in April. 

The Sunday World reports that surveillance footage of the incident supports the employee's claims, additionally showing Murphy picking up a chair in an "aggressive manner". 

Murphy opened the pub in 2007 and is serving his first term as a New Hampshire state senator. 

The Murphy's Taproom website states that Murphy has been in the hospitality industry for 29 years. 

"He opened the original Murphy’s Taproom on Elm Street in Manchester, NH, in 2007, and expanded it three times before opening a huge new location in Bedford in 2017," the website states. 

"A graduate of the University of Baltimore and the University of Maryland, he was a four-term state representative in Bedford before opening his latest venture."