Automotive production fell 44.3 percent in June from a year ago, data from the Asean Automotive Federation show.
Automotive sales also declined 12.5 percent in June, making the Philippines one of the weakest performers in the region this year.
Vehicle production slowed to 40,982 units in June from 73,594 units in the same month in 2017. It followed a 3.5-percent decline in January, 39.3 percent in February, 32.7 percent in March, 34.2 percent in April and 58.7 percent in May.
Automotive sales started out with a shaky 4-percent growth in January, followed by a 3.2-percent decline in February, 22.8 percent in March, 11.9 percent in April and 13.7 percent in May.
Meanwhile, the Philippines posted the highest sales growth for motorcycles and scooters of 25 percent to 768,609 units in the first half from 613,896 units a year ago. Local production of motorcycles and scooters also increased 1.3 percent to 641,647 units as of June from 723,507 units a year ago.