Former Thai Prime Minister Thaksin Shinawatra has resigned as leader of his political party. Scores of top members have already quit the party as the military-backed government starts corruption investigations into Mr. Thaksin and other former officials.

Thai Rak Thai party official Pongthep Thepkanjana told reporters in Bangkok Tuesday Mr. Thaksin had resigned in a letter sent from London, where the former prime minister has been since a coup ousted him two weeks ago.

"He resigned from leader of the party. He deemed that because of the situation it is the responsibility of executive members to resign to pave the way for the party to select new executive members," said Pongthep Thepkanjana.

In his letter, Mr. Thaksin thanked his supporters and said his decision was meant to preserve the future of the party.

But political analysts say Thai Rak Thai has an uncertain future without its founder. Some 200 party members, including high ranking Thaksin government officials and lawmakers, have already quit and the party has been unable to engage in politics since the military takeover.

Mr. Thaksin and some of his cabinet members are under investigation for alleged corruption and the party also faces charges of electoral fraud in last April's snap elections. The ruling military council has banned from politics for five years members of any party that has breached election laws.

The telecommunications tycoon formed the Thai Rak Thai or "Thai Love Thai" party in 1998. It dominated Thai politics from 2001, drawing much of its support from the rural areas where Mr. Thaksin focused most of his economic and social programs such as farm loans and cheap health care.

The military said it was forced to intervene to reunite a nation divided after months of political turmoil. Almost daily protests were held against Mr. Thaksin's alleged corrupt activities, including the controversial sale of his family's telecommunications holdings to Singapore's national investment company. The family allegedly avoided paying taxes on the deal.

On Sunday, the military council installed former army commander Surayud Chulanont as interim prime minister until elections promised for October next year.