The opposition party found the government's spending of last year's central budget questionable, including the use of millions of baht to pay for Prime Minister Yingluck's overseas trips.
The Democrat MPs took turns to deliberate the 2014 Budget Bill on the second day of the budget debate Thursday when sections 4 and 5 were tabled for consideration.
Section 4 relates to the central fund from which the prime minister is authorised to approve spending, while Section 5 involves the PM's Office budget.
During the debate on Section 4, Democrat list-MP Vachara Phetthong proposed that the 343 million baht allocation for the central fund be cut, saying that last year's spending of the fund was a "cause for concern".
Mr Vachara specifically questioned the use of last year's 73.7 billion baht reserve fund for emergency expenditure.
The government had spent 2 billion baht from the emergency reserve to compensate the red shirts held in detention. This was not fair on the other detainees throughout the country, Mr Vachara said.
The government also approved a sum of 200 million baht for Chalerm Yubamrung, who was then deputy prime minister overseeing the Royal Thai Police Office, to quell the anti-government protest by the Pitak Siam group late last year.
"And when the emergency decree was last imposed in three Bangkok districts [between Aug 1-6], was it true that the government approved 400 million baht for its implementation?" he said.
Mr Vachara said national police chief Adul Saengsingkaew spent a total of 600 million baht on preparations to quell protests.
Mr Vachara said while a House committee was vetting the budget bill, the cabinet secretariat did not provide details of how much money had been spent on the prime minister's trips to more than 40 countries.
Vinai Sompong, a Democrat list-MP, proposed that the central fund be cut by 50%, saying he felt the prime minister spent too much money on her overseas trips, particularly on chartering aircraft from Thai Airways.
Democrat MP for Nakhon Si Thammarat, Apichart Sakdiset, criticised the PM's Office's budget request.
He said the PM's secretariat had requested a budget of 500 million baht to follow up on and assess the implementation of government policies, but the secretariat did not say exactly what the money would be spent on.
Mr Apichart said the money should be spent on following up on and assessing the government's first-car buyer programme, its rice-pledging scheme and the budget for the reconciliation push, because these projects are a waste of money, Mr Apichart said.
Foreign Minister Surapong Tovichakchaikul rose to reply on behalf of Ms Yingluck and said the prime minister's visits were at the invitation of those countries. The increasing number of tourists visiting Thailand is a result of the prime minister's overseas trips, Mr Surapong said.
After over 12 hours of deliberation, the House managed to pass the second readings of Section 4 by 291-126 votes, Section 5 (288-133), Section 6 on the Defence Ministry's budget (288-109) as of press time last night.