TAIPEI, Sept 28 (Reuters) - Taiwan's central bank said on Wednesday that in the first half of this year it sold a net $8.25 billion to intervene in the foreign exchange market to try and prop up the Taiwan dollar, compared with buying a net $9.12 billion for all of last year.

It is necessary to maintain the relative stability of the Taiwan dollar exchange rate, the central bank said in a report to lawmakers ahead of its governor taking questions in parliament on Thursday. (Reporting by Liang-sa Loh; Writing by Ben Blanchard; Editing by Andrew Heavens)