TAIPEI - Taiwan's main opposition leader Ma Ying-jeou asked his party to be patient in dealing with beleaguered "president" Chen Shui-bian amid a series of corruption scandals and reiterated a call for Chen's resignation.

Ma - who is widely seen as the front-runner in the island's 2008 elections - said Saturday his Nationalist Party should be cautious about its approach in attempting to remove Chen from office. He said there's a risk that party supporters could be let down if a campaign to oust Chen fails.

Taiwanese protesters wave opposition party flags as they call for "president" Chen Shui-bian to step down over an insider-trading scandal involving his son-in-law in Taipei June 3, 2006. [Reuters]

"We must first think and then act or we could use the people's anger but find out that we are driving them into despair," Ma said in a speech at a party meeting.

Police arrested Chen's son-in-law, Chao Chien-min, last month on suspicion he used insider information to profit from the purchase of shares in property company Taiwan Development Corp. Chao has denied the charges.

"Presidential" Deputy Secretary-General Ma Yong-cheng resigned Thursday following opposition accusations that he was involved in business deals and took favors from executives - accusations that he also denied.

The incidents have damaged Chen's image after he came to power in 2000 partly on promises of clean government after 55 years of Nationalist rule. Recent opinion polls have shown Chen's support slipping to 20 percent.

Ma has faced criticism from within his party for being too slow in taking advantage of Chen's problems.

Some Nationalist politicians have pushed for a campaign to recall Chen, but the procedure needs to win the support of two-thirds of lawmakers - a difficult task since the opposition only holds a slim majority of seats.

Ma said if the campaign to remove Chen from office succeeded, "vice president" Annette Lu would take over the reins and no real change would be achieved.

Ma suggested a no-confidence motion could be filed, which if successful would force new legislative elections within two months.

The opposition leader drew applause during his speech after reiterating his call for Chen's resignation. "President Chen should seriously consider resigning immediately," Ma said.

Ma later addressed a crowd of 3,000 protesters at a rally organized by the People First Party - a Nationalist ally - outside the "presidential office" building. He joined in shouts of "Down with A-bian" - a reference to Chen's nickname - but still didn't specify which course of action his party would take.