David Thake has resigned from the St Paul's Bay local council, saying that he could no longer represent the Nationalist Party, given his views on Adrian Delia as its leader.
Mr Thake, who is in London, said he was astonished that the letter was leaked within an hour of being sent.
"I called the mayor and the executive secretary, but I was not going to say anything until I had officially resigned," he told the Times of Malta.
"I think that this is the right thing to do as I was elected to the council on the PN ticket and they should be allowed to choose someone else.
"My position is very clear: Adrian Delia has too many unanswered questions and allegations hanging over him and is therefore not fit for purpose, especially at this time in our history," he said over the phone.
"It is up to the party to see whether it agrees with my assessment that the leader should be changed."
Mr Thake, who was the deputy mayor of the council, wrote to Dr Delia as follows:
"I have just informed the Mayor of my Local Council that I will be tendering my resignation from the local council.
This resignation will be handed in to the acting executive secretary at the end of the next Council meeting.
My position as a local councillor on the PN ticket is - in my opinion - no longer tenable given my views on your suitability as leader of the PN.
I wanted to be the person to give you the information directly but I understand that the Mayor has already circulated my intentions."
Mr Thake had a popular radio show and contested the June 2017 elections on behalf of the Nationalist Party.
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