After hearing the rebuttals, the Senate committee in charge of scrutinising the 10 candidates will decide whether to recommend them for the job by September 3, Suthorn said.

Out of the 21 agencies tasked to verify the candidates' records, 12 had completed the checks with favourable results to the candidates, he said.

The Senate will ask the candidates to address only signed complaints and discard all hearsay and anonymous tips, he said.

Earlier, the scrutinising committee said it had received some 154 complaints via the postal service, 133 of which were related to alleged partisanship. Another 230 complaints were messages posted on the upper chamber's web board.

Two candidates, Kaewsan Atibhodi and Wasant Soipisut, appear to face most questions about their political impartiality. Kaewsan said he was ready to explain away any doubts on his impartiality.

Commenting on the question of impartiality, caretaker Senator Thongbai Thongpao said although Kaewsan had expressed critical views against the caretaker prime minister, this should not be construed as partisanship.

"Kaewsan is free to express his personal opinions and can still be politically impartial," he said.

Thongbai also stated that another candidate, Nam Yimyaem should not be portrayed as an anti-government figure after he uncovered the electoral fraud involving the Thai Rak Thai Party.

"Nam was appointed to lead the investigation by the EC and did not act with a grudge toward the ruling party," he said.

Caretaker Senator Sawai Phra-manee said he foresaw no hurdles in vetting the candidates' qualifications, saying the Senate could meet the deadline to pick five candidates.