A Democrat MP Thursday sliced open a bag of the government's pledged rice in parliament in a bid to demonstrate shoddy quality control of the stored paddy.
Warong Dejkitvikrom, the MP for Phitsanulok, said the rice, retrieved from Surin, was brown and rotten.
His display in the House drew protests from government lawmakers.
The government will not be able to maintain the quality of the pledged rice, Mr Warong said, questioning the Commerce Ministry's handling of the programme.
Alleged irregularities in the scheme highlighted the session.
The sack had all the necessary codes showing its origin and production year, but lacked details of the rice mill, Mr Warong said.
The rice came from a government warehouse, he added.
The Pheu Thai-led government had also failed to explain the details of its government-to-government (G-to-G) rice deals, he said.
The government had said it needed time to investigate the alleged irregularities involving the G-to-G contracts, but it has since provided no explanation, he said.
Only rice mill owners benefit from the scheme, he said.
He claimed many rice mills belong to people affiliated with the ruling Pheu Thai Party while warehouses storing the pledged rice are operated by the government.
He challenged the government to open up its warehouses to reporters so they could see for themselves.
Deputy Commerce Minister Nattawut Saikuar insisted the rice pledging scheme is run in a straightforward and transparent manner.
A committee is investigating the corruption allegations involving the scheme, Mr Nattawut said.
The committee had submitted its initial findings to the commerce minister, but the minister had told the panel to make additional inquiries and submit its findings within 90 days.
The committee has not provided an explanation because it has not yet finished its work, Mr Nattawut said.
The investigation is looking back over a three-year period, he said.
Mr Nattawut said the government is trying to maintain rice quality.
There are huge quantities of stored rice and it is impossible to ensure all the rice is in perfect condition, he said.
Mr Nattawut fired back at Mr Warong, asking how he gained access to the government's warehouse to take the sack of rice.
He accused Mr Warong of trespassing and said he would instruct the Internal Trade Department to lodge a police complaint against him.
Mr Nattawut said Pheu Thai Party MPs have also asked the Department of Special Investigation to look into alleged irregularities involving the release of rice stocks during the tenure of the previous Democrat Party-led government.
Previously, the National Anti-Corruption Commission (NACC) had decided to look into suspected irregularities involving the scheme.
The NACC's move came after the Democrat Party submitted a petition along with evidence asking the NACC to investigate the rice pledging scheme.