Ali, who is a former military governor of Kaduna State, agreed to appear before the Senate, but declared that he is not employed to wear uniform.
He told TVC that rather he was appointed to work effectively.
He was summoned by senators over the new order by the Customs Service for all old vehicles to pay their customs duty.
Customs offered a 60 per cent rebate for vehicles from 2015 below.
Speaking in an interview on TVC, Ali said: “Let me say I will appear before the Senate. With regard to uniform, certainly no.
“Why is it so? I was not appointed to wear uniform. I am sorry to say, I don't know why Senate is talking about uniform.”
The Senate, in a motion raised by Senator Dino Melaye on Thursday, summoned him to appear before it in uniform to explain why Customs has not suspended its Customs policy on vehicle duty despite the directive of the lawmakers.
But, according to him, what should be a concern to the National Assembly in its oversight function, is whether he is performing his duty, and “not whether I am in uniform or not.”
He, however, noted that at the time of the interview, he was yet to receive any letter of invitation from the Senate.
His words: “There is a procedure for inviting members of the executive to appear to the Senate. If that procedure is followed, we will abide by that procedure. No member of the executive is invited on media network ,either on the television or the radio. If they follow that procedure, we will appear before them.
“Up to this moment, I have not seen any correspondence from the Senate in my office.”
Explaining the genesis of the vehicle duty policy, he said that upon the ban of importation of vehicles through land boarders, the Association of Motor Dealers of Nigeria (AMDON) confessed that they had cars that were smuggled into Nigeria.
The dealers, according to him, sought for assistance which led to the issue of creating a vehicle seats for their regularization.
Ali said: “We said that all the vehicles that were smuggled, you will bring them to a vehicle seat and regularize them. We said we would help, but you must pay the duty.”
He defended his appointment as Comptroller General from outside the Customs saying: “In that same law, it says that there shall be deputy comptroller-generals appointed by the President of the Federal Republic of Nigeria from among the Nigeria Customs Service.
“So that gives you a very clear cut that today or any day, the President of the Federal Republic of Nigeria can decide to appoint a Comptroller-General outside the Nigeria Customs Service, but it cannot appoint Deputy Comptroller Generals outside the Nigeria Customs Service.”
He also claimed that some motorists use only one number plate to drive up to 20 vehicles.