The anti-corruption commission has been compelled to make public its findings on the fake travel and sitting allowances scandal in Parliament.
The National Civil Society Congress on Tuesday threatened to move to court to compel EACC to publish results of their investigation.
In December last year, the commission revealed that several former MPs were still receiving salaries despite losing their seats.
EACC's audit report, handed over to National Assembly Speaker Justin Muturi, stated that the Public Service Commission had not updated its payroll, leading to payment of salaries to former MPs.
The lobby group now intends to petition EACC, the Director of Public Prosecutions, and the Speaker to take action against legislators found to have taken part in corruption.
"This Sunday, the NCSC will officially launch the petition. We expect that the undersigned and the Rev Timothy Njoya will officiate the function," a statement from the group read in part.
Muturi has also in the past questioned the payments of mileage and sitting allowances to lawmakers, terming them as "worrying".
He urged anti-graft body to double-check.