The Democrat Party also rejected fresh calls to sack the foreign minister over his own links to the week-long blockade of the airports in November to December, which caused major damage to the economy.

The appointment of the three members of the People's Alliance for Democracy (PAD) is a new blow to supporters of ousted former premier Thaksin Shinawatra, whose allies were driven from government partly as a result of the siege.

Suthep Thaugsuban, deputy prime minister and Democrat party secretary general, said the three advisers were 'not core leaders but merely joined the PAD to carry out their political movement'.

Local press reported that the PAD leaders would be endorsed in a cabinet meeting on Tuesday.

Samran Rodpetch was expected to be named as secretary to the Science and Technology minister, while Prapanth Koonmee and Phichet Pattanachot would be advisors to the deputy commerce minister and public health minister.

The royalist PAD occupied the airports at the peak of their protest movement against the previous, pro-Thaksin government, stranding hundreds of thousands of foreign travellers and costing the economy billions of dollars.

They abandoned the siege after the Constitutional Court disbanded the former ruling People Power Party on December 2. Democrat Party leader Abhisit Vejjajiva won a parliamentary vote to become prime minister on December 15.

Thaksin supporters known as 'red shirts' because of their favoured attire have since held several noisy protests focusing on the role of new foreign minister Kasit Priromya, who regularly delivered speeches at PAD rallies.

Mr Suthep however dismissed threats from Thaksin loyalists to disrupt next month's Association of Southeast Asian Nations summit in Thailand if Mr Kasit is not removed from the government.

'The red-shirt people allege that Kasit is a terrorist, but Kasit is a diplomat who can benefit our national interests,' Mr Suthep said. -- AFP