A Taiwanese warship visited disputed fishing grounds on Tuesday, after Taiwanese fishermen complained of harassment by Japanese patrol boats.
Japanese patrol boats often stop Taiwanese fishing vessels
Defence Minister Lee Jye and a group of MPs including speaker Wang Jin-pyng were aboard the frigate, which visited the area around the Diaoyu Islands.
The islands, known in Japan as the Senkaku, are claimed by Taiwan, China and Japan.
The frigate returned to Taiwan without incident.
Mr Wang said Taiwan had the right to defend its sovereignty.
"This area belongs to us historically, geographically and legally," he told reporters before boarding along with a cross-party group of 15 MPs.
"We must defend our sovereignty and protect our fishing rights."
A military spokesman, Liou Chih-chien, described the voyage as an "inspection tour" and said that while the frigate would enter disputed waters it would not approach the actual islands.
The Fengyang frigate is armed with air defence missiles and will be escorted at a distance by other Taiwanese ships and aircraft, the officials added.
Opposition politicians in Taiwan have criticised the government for failing to stand up to Japan.
"The entire nation is waiting for the government to show its guts and stand up to Japan," said one independent MP, May Chin.
The dispatch of the Fengyang comes after 50 Taiwanese fishing boats staged a rare protest in the disputed area earlier this month.
They were protesting at being frequently driven out of the waters by Japanese patrol boats.
Some Taiwanese fishermen have reportedly called for protection from China, Taiwan's arch-rival.
One unnamed fisherman told a Taiwanese TV station he was please to see the frigate being sent out.
"It's good to see it's finally our turn to scare the Japanese - they have always bullied us and make us feel we are thieves at sea," he told cable news network TVBS.