A former Federal Court judge has rapped chief secretary Ali Hamsa's threat against civil servants participating in the Bersih or red-shirts rallies tomorrow as unconstitutional.

Retired judge Gopal Sri Ram was reported by Free Malaysia Today saying civil servants had a right to exercise their constitutional right to assembly as long as it did not interfere with their professional duties.

“Participation in a rally is a right conferred under article 10 of the Federal Constitution and any restriction is absolutely void,” Sri Ram was reported saying today.

Ali yesterday said the Public Services Department would not hesitate to act against civil servants who are captured in photographs of the rallies published by the media, according to Bernama.

He said those found involved in the rallies face disciplinary action including a pay cut or sacking.

According to FMT, Sri Ram said the order was a "disproportionate incursion against a constitutional right".

“You do not use a sledgehammer to kill a fly and the response from Ali is not proportionate to the harm intended to be dealt with,” he was reported saying.

“The circular is like administering a poison to cure a common cold."

Therefore, he said, the order is null and void.

Bersih will hold its fifth rally tomorrow at Dataran Merdeka to call for electoral and democratic reforms, and in particular, for the resignation of Prime Minister Najib Razak over the 1MDB scandal.

In response, Sungai Besar Umno chief Jamal Md Yunos has vowed to hold a counter-rally concurrently to stop Bersih 5 from proceeding.

Yesterday Najib expressed concerns of a possible clash between the two, cautioning that rallies such as the Arab Spring had not brought change as the people had wanted, but only "misery".

However lawyer Eric Paulsen reminded the police that Section 18 of the Peaceful Assembly Act 2012 requires the police to assign separate venues and dates for counter-rallies if conflict is expected.