A claim by Uttaradit Senator Peerasak Porchit, the acting second Senate deputy speaker, that some members of the Upper House went to Singapore last week to meet former prime minister Thaksin Shinawatra was not true, Pheu Thai spokesman Nopporn Nopparit said on Sunday.
Mr Nopporn said his party had checked Mr Peerasak's claim and found no substance to it.
He dared Mr Peerasak to produce evidence to prove his claim.
The Pheu Thai spokesman also denied as groundless an allegation by the People's Democratic Reform Committee (PDRC) that Thaksin had paid 35 senators 200 million baht each to vote down a Senate bid to appoint a neutral prime minister.
"If senators could be bought with 7,000 million baht, Surachai Liangboonlertchai would not have been elected Senate speaker. It is an accusation laid by people who have never got over Thaksin," Mr Nopporn said.