Deputy Home Minister Nur Jazlan claimed that "anarchist groups" joining the Bersih rally will attempt to provoke the police into using force against protesters.
"The provocation will be so that police can be blamed when force is used on participants of the illegal rally so as to incite hatred on the authorities and government," he said in a statement today.
Nur Jazlan likened this to the Bersih 3.0 rally in 2012, where police responded with fury towards the end of the rally when some protesters, purportedly on the instructions of political leaders, breached the barricade at Dataran Merdeka.
"I see similarities with the Bersih rally in 2012 where the participation of opposition political parties ruined the rally's goal of a peaceful assembly after there were disturbances.
"What the illegal rally organisers claim to be freedom of assembly and noble intention are merely lies as it has been proven to have been perpetrated by the opposition," he said.
Nur Jazlan also urged the public not to participate in the protest.
"I hope the people will not be fooled into joining the Bersih 4 illegal rally as the likelihood of disturbances is high as we do not know the background of the participants who may comprise groups who are out to take advantage and create chaos.
"It is for this reason police do not agree with the demonstration as there is no clear person who can be held responsible for any injuries or damage to public property," he said.
Nur Jalzan said some 4,000 police officers would be mobilised to maintain public order during the protest, estimating that the cost would run into millions.
The Bersih 4 overnight rally is to take place in Kuala Lumpur on Aug 29 and 30.
Protesters are calling for Prime Minister Najib Abdul Razak to step down, as well as other reforms.
Najib is plagued by several scandals, including his handling of debt-ridden 1MDB and the deposit of RM2.6 billion into his personal bank accounts.
The RM2.6 billion has been described as political donation, while the prime minister has repeatedly denied using public funds for personal gain.