The former prime minister said it was only secondary for the coalition as to whether the elections were clean or not.
“Its objective is to tarnish the Government's name and the police, so that the Opposition will win.
“Their purpose is political in nature, particularly for Pakatan Rakyat,” Dr Mahathir said.
“They want to paint the Government black and, although you are grey, you look more white,” he said.
He added that Bersih wanted a repeat of the 2008 political tsunami that saw the Opposition take over five states.
After studying the coalition's demands, Dr Mahathir concluded that Bersih was only using the rally to attack the Government.
He said the country's elections were clean and fair as Opposition leaders were also able to win.
He warned all parties of possible clashes during July 9 rally, which could disrupt the peace in Malaysia.