The Salaries and Remuneration Commission (SRC) on Friday filed a fresh law suit against all members of the 12th Parliament.
SRC Chair Lyn Mengich had previously warned about the court action as she explained why the Sh250,000 monthly housing allowance MPs awarded themselves was illegal.
"Payment of the house allowance to MPs and senators amounts to double payment of a benefit which is already included by SRC in the gross pay.
"The unconstitutional action by the Parliamentary Service Commission to pay MPs and senators house allowance of Sh250,000 monthly will cost taxpayers an extra Sh104 million every month, which is Sh1.2 billion annually," she stated.
In April, the MPs each received Sh2.25 million additional to their monthly salaries.
The amount was backdated to October 2018 when the MPs approved the extra allowances to take effect.
National Assembly Speaker Justin Muturi, however defended the move stating that a ruling by High Court Judge Chacha Mwita had allowed them to get the allowance.
"The recent PSC determination to provide a housing benefit to MPs was well guided by Justice Chacha Mwita’s ruling of October 5, 2018, which established that state officers qualify for this benefit.
"It is a matter of fact that MPs are state officers and it would be unfair to be prejudiced against them," he stated.