Making a special statement to media, the President said he informed the UPFA leaders including Dinesh Gunawardena and Vasudeva Nanayakkara that he was against granting nominations to the defeated president.
"I continue to stand against Mahinda Rajapaksa," the President said. "He will be defeated again," he asserted.
He noted that some have criticized him for taking the leadership of UPFA but all his government achieved was possible because he was the president of UPFA and its main constituent party, Sri Lanka Freedom Party (SLFP).
The President added that if he resigned from the leadership of the party, anyone Mahinda Rajapaksa wanted would have received nominations for the elections.
If the SLFP wins the elections there are other SLFP seniors who could be appointed as the Prime Minister, the President said.
However, the UPFA has already indicated that Mahinda Rajapaksa will be the Prime Minister if they secure the parliament at the August 17th elections.
President Sirisena expressing his commitment to conduct a free and fair election said whoever wins the next election his sincere wish is that they would implement the wishes of those who voted for him on January 8th.
The President, who faced severe criticism for his decision to allow the party to nominate Rajapaksa, said during the past two weeks he was called every possible name and labelled him as a traitor.
President Sirisena said he applauds those who criticize him as criticism is an important aspect of a democracy.
However, he cautioned that although he was happy that he was able to restore the freedom of expression in the country, that freedom should be enjoyed with a sense of responsibility.