TITUSVILLE, Fla. — A Republican state lawmaker charged with offering to perform oral sex for $20 on an undercover male police officer vowed Thursday to defend himself in court and said he would not resign from office.

“I am filing a not guilty plea. I am vigorously going to fight this,” state Rep. Bob Allen, a co-chair of Republican presidential candidate John McCain’s campaign in Florida, said at a news conference. “I am not resigning my office because the people elected me and want me to do a good job. I am going to do a good job for them in finishing this term.”

Allen called his arrest “an ugly and unpleasant situation that has been thrust on me and my family.” The lawmaker had sponsored a failed bill that would have tightened the state’s prohibition on public sex.

He choked up when he thanked backers who had contacted him to offer their support. He warned people not to jump to conclusions about what happened but said he could not offer any details about the arrest because of his legal strategy. Allen is married and has a teenage daughter.

“It is not true. It is inaccurate and therefore, it’s not guilty,” Allen said.

Republican Party of Florida Chairman Jim Greer said the matter would be addressed in a timely and appropriate matter.

“While this is an extremely serious matter, the House of Representatives and the judiciary system have established a process to deal with situations of this nature,” Greer said in a statement.

However, House Speaker Marco Rubio said in a statement that because the charge against Allen is a misdemeanor, not a felony, “the House rules don’t provide for a specific response in the event that he is found to be guilty.”

“The charge against Rep. Allen is serious,” Rubio said. “We will continue to monitor the situation and take appropriate steps if necessary.”

Allen’s arrest on Wednesday came days after a key Southern supporter of McCain opponent Rudy Giuliani, U.S. Sen. David Vitter of Louisiana, was identified as a client of a Washington, D.C., escort service.

“It just seems sad and tragic,” Gov. Charlie Crist said Thursday when asked in Miami about Allen’s arrest.

Veteran’s Memorial Park was under surveillance when Allen was seen coming in and out of a restroom three times, said police Lt. Todd Hutchinson. Allen, 48, then approached an undercover officer and was arrested.

He has been charged with solicitation for prostitution, which has a maximum penalty of one year in jail. Brevard County jail officials said Allen posted a $500 bond.

While being transported to jail, Allen told WFTV Channel 9 that the situation was “a very big misunderstanding.”

Allen was elected to the Florida House in 2000. He was chairman of the House Committee on Energy.

Allen was named in March as one of six co-chairs for McCain’s Florida campaign.