In a separate case, Ko and the TPP have also acknowledged that campaign funds during the presidential campaign were misreported.
Ko said last week he would temporarily step down as party chairman while that case is investigated and apologised to party supporters.
Ko has been widely expected by Taiwan media to seek the presidency again at the next election in 2028.
But opinion polls have shown that the campaign fund scandal in particular has hammered support for him and the TPP, which he founded in 2019 in an attempt to create a third force in Taiwanese politics.
The TPP has only eight lawmakers in Taiwan’s 113-seat parliament but has an outsized role as neither the ruling Democratic Progressive Party (DPP) nor the largest opposition party, the Kuomintang (KMT), has a majority.
The TPP and KMT joined forces this year to push through reforms to give parliament greater oversight power that prompted mass protests.
Those reforms, opposed by President Lai Ching-te’s DPP, are being reviewed by Taiwan’s constitutional court.
