The Lagan Valley MLA accused his party of “losing its way” since he had joined it and said he would be defending his stance.
However, he confirmed he would not be attending a disciplinary committee hearing scheduled for Friday.
“I can confirm that I received a letter asking me to turn up at party headquarters on Friday but I can’t make it because I have a pre-arranged family commitment in Scotland. I will be asking for a different date,” he said.
The hearing follows a decision by party leader Mike Nesbitt to withdraw the Assembly whip from him in a row over his position on the flying of the Union flag at Belfast City Hall.
Mr McCrea fell foul of the party hierarchy when he publicly opposed the stance of the UUP’s three Belfast City councillors, who voted to keep the Union flag flying over Belfast City Hall all the time.
Since there were more nationalists on the council and an equality impact assessment had recommended a reduction in flag flying, Mr McCrea believed a compromise was inevitable.
He pointed to a UUP policy document which accepted flag flying on designated days. This compromise was proposed by the Alliance Party and eventually accepted by nationalists, who originally wanted the flag removed altogether, but not by unionists.
Mr McCrea stated that Alliance had been correct and he would have voted with it if he had been there.
In response, the three Belfast councillors threatened to resign unless he was disciplined, and Mr Nesbitt moved to remove the whip from Mr McCrea. This effectively removed him from the party’s Assembly group until further notice.
There is some surprise that a further sanction is being proposed.
A party source with knowledge of the case said : “This is a full disciplinary hearing. It follows a complaint in writing from a particular constituency association which I am not prepared to name.”
He added that the complaint alleged “a breach in policy, a breach in confidence and failure to consult the Press office or give it notice of his statement”.
The disciplinary committee has the power to take any action against Mr McCrea, including expulsion from the party or fining him.
Its members include Tom Fleming, who signed the letter, Lord Rogan, Lady Trimble, James Cooper and May Steele.
The committee reports its findings to the party officers.
Mr McCrea showed no signs of submitting meekly to censure. He intends arguing his case forcefully and publicly.
“I voted yes to the Good Friday Agreement and I entered politics because I believe in a shared future. I just wonder if the party has lost its way since then,” he said.
He went on: “I first voted Ulster Unionist at the time of the referendum on the Belfast Agreement. I later joined the UUP to find a way forward that encompassed the spirit of the Agreement and I shall be asking the party if those principles are what it still believes in.”
Audio: McCrea tells Nolan that Alliance were right on flag issue December 2012