The Department of Petroleum Resources (DPR), and other government agencies monitoring sales of petrol at filling stations have been urged to extend the exercise beyond 4p.m. everyday.
Nigeria Union of Petroleum and Natural Gas Workers (NUPENG), made the call during interview with News Agency of Nigeria (NAN), in Lagos on Sunday.
Alhaji Tokunbo Korodo, South-West Chairman of the NUPENG, who made the call, said some filling stations sold only at night when monitoring agencies had closed for the day.
"They take advantage of darkness to dispense fuel above the official pump price of N86.50 approved for independent marketers.
"These filling stations also take advantage of the fact that major marketersí filling stations around them are not dispensing to sell a litre at between N110 and N120," he said.
"Some greedy marketers have enough petrol in stock. They pray or the price to go up in the New Year as usual, not minding that the Federal Government had regulated the price.
"So, it is now impossible for them to sell in daylight because of enforcement going round. They have decided to be selling very early in the morning and late in the night when enforcement teams have gone home.
"These filling stations are located mainly in the outskirts of Lagos and they are mainly independent marketerís filling stations.
"If DPR and other relevant agencies can extend their enforcement hours to evening period they will catch up with them.
"I think full enforcement and if possible seizure of their licenses and closure of their filling stations will serve as deterrent to others," he said.
He, however, objected to calls for the sale of the nation's refineries but rather advised government to intensify efforts at revamping them and to increase the daily production and build modular refineries to back them up.