The Malaysian Communications and Multimedia Commission (MCMC) has received brickbats for wanting to block websites promoting Bersih 4, with critics calling it a futile attempt.
"The world knows that there is going to be a Bersih 4 rally this weekend, not only in Kuala Lumpur, Kuching and Kota Kinabalu but in at least 50 cities worldwide.
"Is the MCMC going to act and pretend that the Bersih 4 rally in Kuala Lumpur does not exist, by wiping it out of the telecommunications system?
"This is a most shocking manner to cope with challenges of the information age," said DAP supremo Lim Kit Siang in a statement.
Instead, Lim said the government should facilitate the rally by boosting mobile communications in Kuala Lumpur, as it is expected to become cluttered due to the large number of protesters.
MCMC's move came just two days after newly-minted Communications and Multimedia Minister Salleh Said Keruak said the internet would only be monitored.
Lim said Salleh should be held responsible if there is a crackdown on communication during the protest.
Meanwhile, former deputy minister Saifuddin Abdullah also criticised MCMC's move.
"They (authorities) will use whatever means to stop Bersih 4: block the internet, declare it illegal, intimidation. Fight on Bersih," he said.
Lawyers for Liberty executive director Eric Paulsen said the move was symptomatic of the government's "inability to deal with freedom of speech and information".
"Rather than coming to the terms (with) and embracing the Internet and social media age, such regressive actions only make the authorities appear clueless and disconnected with the people.
"Information will still be shared and the authorities must learn that the bad old days where they can control information is long gone," he said.
The overnight Bersih 4 rally on Aug 29 and 30 will call for the resignation of Prime Minister Najib Abdul Razak and sweeping reforms.
Najib is plagued by several scandals, including his handling of debt-ridden 1MDB and the deposits of RM2.6 billion into his personal bank accounts.
The prime minister had denied taking government funds for personal gain while his supporters claim the money was political donation from the Middle East.