MANILA, Feb. 6 (Xinhua) -- Philippine President Rodrigo Duterte on Tuesday told the government workers including government officials to travel on economy class when they are on official trips.

Duterte said official trips are funded by the government. "Because it is not our money, so you take the cheapest," he said in a speech during the founding anniversary of the Bureau of Customs in Manila.

He said those who wish to take business class should shoulder the extra costs.

"You want comfortable (trip)? You add, if you have the money," Duterte said.

Officials who upgrade their tickets will have to explain to him, he said. "Show me the receipt that you added more to be upgraded there. Because it is not our money."

Duterte reiterated that he would not hesitate to fire government officials caught making unnecessary, lavish trips abroad.

Duterte has earlier fired Maritime Industry Authority Administrator Martial Amaro for making 24 trips in just 18 months in office. Before Amaro, he also fired Presidential Commission for the Urban Poor Chairman Terry Ridon also for making several official trips abroad.

Earlier this month, Duterte issued a memo imposing stricter rules on official foreign travels in a bid to curb "extravagant and lavish" trips.

Those official or personnel who do not comply with the new directive could face administrative charges, the memo warns.