The opposition Move Forward Party (MFP) says the government has not given it enough time to study the 2024 budget bill ahead of its first reading on Jan 3-5.
MFP leader, Chaithawat Tulathon, who also heads the opposition bloc, said the government had given the opposition just seven days to study the bill's details.
"This is the least amount of time given to the opposition to study the budget bill in several years. It is unreasonable.
"The seven-day period also covers the New Year holiday. But we will do our best to study it, anyway," he said.
Mr Chaithawat added that when Pheu Thai was in opposition, the Prayut Chan-o-cha government allocated 14-17 days to study budget bills, which was also considered too little.
"MPs from both government and opposition camps should have enough time to study the measure.
"Even though it was not initiated by the current government, budget spending under the bill still needs to be reallocated in response to this government's policies.
"That's why we have to scrutinise the government's budget reallocation," Mr Chaithawat said.
The budget bill for the 2024 fiscal year seeks a total of 3.48 trillion baht. The bill, which is supposed to take effect on Oct 1 every year, has been delayed because the new coalition government needed to find its feet first.
United Thai Nation (UTN) Party spokesman, Akaradej Wongpitakroj, said deliberation of the budget bill should not be delayed any further as funds need to be disbursed as quickly as possible to stimulate the economy.
He said the party's MPs have been asked to spend their New Year holiday studying the bill ahead of the debate for the sake of the country's future.
Mr Akaradej added that two veteran UTN lawmakers -- Witthaya Kaewparadai and Juti Krairiksh -- will instruct other party MPs in how to debate the budget bill in parliament.
The UTN will be allocated four seats on the scrutiny committee, he said, adding the party will meet on Thursday to select party members qualified to sit on it.
The budget bill debate will take place Jan 3-4 and the vote will be held the following day before a 72-member House committee is formed to vet the bill.
Cabinet ministers and government MPs will be allocated 20 hours, as will opposition MPs.
According to a government source, the cabinet will send an electronic budget bill file to MPs online to study today.