Senate President Bukola Saraki has condemned Tuesday's raid on Edwin Clark's home in Abuja by personnel of the Nigeria Police Force.
In a statement on Wednesday, Saraki described the raid as a "gross abuse of state institutions", saying it shows that "something is amiss".
"The unwarranted harassment of Chief Edwin Clark, who is known for being very vocal in expressing his views on national issues, at a time when the nation is preparing for elections does not reflect well on the country," he said.
He also decsribed such actions as constituting a "threat to democracy".
"Chief Clark, who is also a Second Republic Senator and former minister under the General Gowon administration is not above the law," Saraki said.
"If there is a genuine reason for his home to be searched by law enforcement agencies, nobody will object to it. However, as it appears now, for the Police to conduct a raid on the home of a man of that age on the pretence that they were looking for arms and eventually — the claim turned out to be a hoax — means that something is amiss.
"These actions represent a gross abuse of state institutions."
Noting that since the Inspector General of Police had denied authorising the raid, the next move "should be a thorough, transparent investigation into the Senator Edwin Clark incident to prevent future reoccurrences".
He credited the previous administration with the "peaceful change in 2015", saying it was because the government in power allowed democracy to work.
"If the government had allowed the flagrant abuse and misuse of state institutions to be the norm, we would not have had the change that occurred," Saraki said.
"Democracy is not only about elections. Circumstances that will create tension in any part of the country or make people feel that their fundamental human rights are being trampled upon should be avoided.
"If a man of the caliber and status of Senator Edwin Clark can suffer such an unwarranted raid on his home, then what will happen to ordinary Nigerians as we move towards the 2019 polls and beyond?"