Taiwan's relations with Japan have regressed since the Nationalist Party came to power, but they are likely to rebound, parliamentary speaker Wang Jin-pyng said in an interview.

"Relations were at their highest because of the government of the Democratic Progressive Party . . . and suddenly the (Nationalist Party) came to power and so many problems have emerged — it's like relations relapsed significantly in an instant," Wang told foreign media after returning from Japan on a fence-mending visit earlier this month.

His comments mark the second time a top Taiwanese politician has openly warned of deteriorating relations between Taipei and Tokyo.

Nationalist Party Chairman Wu Poh-hsiung said in July "cracks" had begun to appear in the relationship.