The letter, endorsed by well-known businessmen, including Prasarn Maruekapitak and Wuthipong Pribjriwat, cited 10 reasons for Thaksin to refrain from taking office after the April 2 poll.

"Thaksin should pause his political career so as to allow a transparent review of his conduct," the open letter said.

For the past five years, Thaksin's alleged misrule was evident in his self-serving abuse of state mechanisms, the sale of strategic businesses to Singapore, the tax-free sale of Shin Corp and the conflict of interest via Shin shares held by Ample Rich Investment, it said.

Other shortcomings included rampant corruption, exploitation of state power to serve vested interests and blatant attempts to cling to power, the note said.

Senator Kaewsan Atibhodi said he would distribute 50,000 copies of his white paper exposing Thaksin's flawed leadership, dubbed "Thaksinism".

The white paper was a direct critique of Thaksinism, which he likened to a cancer for democracy.

Under Thaksinism, charter provisions were manipulated in the name of democracy, resulting in divisiveness, widespread corruption and instability, he said.

The Democrat Party, meanwhile, characterised the caretaker prime minister yesterday as a shell-shocked leader overwhelmed by the numerous attacks against him.

Thaksin appeared to have lost touch with reality, party spokesman Ong-art Klampaiboon said.