Surapong insisted Asean leaders kept each other informed about key events in their countries.

"Thaksin wanted to explain to his counterparts about his decision for leave of absence," he said.

Thaksin's letters to nine Asean leaders focused on his break before resuming work in the next government while his correspondence with the American leader expressed optimism for democratic rule to prevail, Surapong said.

The caretaker prime minister also wrote a reply to a query from the Australian government about the political situation, he said.

The spokesman said Thaksin presented his views of the domestic situation to foreign leaders, noting that government critics might have a different take on the matter.

He urged critics to debate the contents of Thaksin's letters instead of making innuendoes involving the monarchy in the matter.

The three main opposition parties held a joint press conference yesterday to denounce the letter Thaksin sent to US President George W Bush on June 23, which they described as "back-stabbing".

Thaksin had distorted the political situation in his letter and committed serious misconduct, the Democrat, Chat Thai and Mahachon parties said.

"It is inappropriate for Thaksin to maliciously distort the situation. This is like a stab in the back with one-sided story," Democrat deputy leader Jurin Laksanavisit said.

Jurin said Thaksin portrayed his victory in the April 2 election in a good light even though the Constitution Court had nullified the results after finding the electoral process marred by unfairness and dishonesty.

Thaksin said the opposition parties boycotted the poll because they feared losing when the actual reason was his decision to dissolve the House without any justification, Jurin said.

Chat Thai deputy leader Somsak Prissanananthakul said Thaksin was telling a half-truth when he claimed he resumed caretaker duties because the public demanded he end his leave of absence.

Chat Thai Party leader Banharn Silapa-archa was among those who called for Thaksin to resume his duties under the condition that he adhere to strict ethical standards and quickly hand over the reins to the next government, Somsak said.

Thaksin's letter made his comeback appear to be the result of popular demand, he said.

Democrat Party deputy secretary-general Korn Chatikavanij said Thaksin clearly wanted foreigners to interfere in Thai politics to help him cling to power.

The reply from President Bush was actually a snub because it omitted any mention of Thaksin's political plight, Korn said.

Meanwhile, the Law Society of Thailand issued a statement calling on Thaksin to apply for a royal pardon for his error in referring to himself as the prime minister of Thailand instead of the "Kingdom of Thailand".

People's Alliance for Democracy spokesman Suriyasai Katasila said Thaksin acted in a shameful manner by blaming everyone but himself for the political crisis.

"In writing to President Bush and other foreign leaders, Thaksin appears to be wooing sympathy from the international community in case he decides to crush his opponents [by force]," Suriyasai said.