Prime Minister Yingluck Shinawatra must clearly state whether she and her government support the reconciliation bill, Democrat Party and opposition leader Abhisit Vejjajiva says.
The bill was proposed by 2006 coup leader Sonthi Boonyaratglin, leader of the Matubhum Party.
But Mr Abhisit said the ruling party has a majority in the Lower House and it was illogical to assume the party did not have a hand in the matter.
He said the rule of law could be undermined if the bill is given passage. Those who commit offences would flout laws openly as they would know that if they rose to power, they could push for legislation to whitewash their crimes.
Democrat list MP Ong-art Klampaibul and Democrat MP for Rayong Sathit Pitutecha yesterday submitted a letter to Parliament President Somsak Kiatsuranon to ask him to take the bill off the House agenda tomorrow and Thursday. The legislation has been listed as an "urgent agenda" item.
Mr Ong-art said the contents of the bill are inappropriate and also incomplete as the signatures of some Chartthaipattana MPs who signed a petition to push for the bill had been found to be invalid.
Hasty moves to push for passage of the bill could violate the constitution, Mr Ong-art said.
Pheu Thai spokesman Prompong Nopparit said Pheu Thai MP Samart Kaewmeechai will today table the party's version of the reconciliation bill to parliament.
Mr Prompong said Deputy Agriculture and Cooperatives Minister Nattawut Saikuar, a co-leader of the red-shirt United Front for Democracy Against Dictatorship, will submit another version of the bill on behalf of the UDD to parliament.
Science and Technology Minister Plodprasop Surasawadi said he supports the reconciliation bill proposed by Gen Sonthi because it is against the use of military power to topple a government.
Mr Plodprasop, a Pheu Thai deputy leader, said he believed the party would also support the bill, which would help prevent future coups, even though party members still held differing views on it.
He brushed aside a plan by the yellow-shirt People's Alliance for Democracy to launch street protests against the bill.
Mr Plodprasop labelled the opponents of the bill as advocates of coups. He declined to comment on a suggestion that former prime minister Thaksin Shinawatra stands to benefit.
Gen Sonthi said he will today explain why he proposed the bill.
He said the proposal was not made solely by him, but by a committee. Gen Sonthi said the bill was only a road leading to reconciliation, which is the target, and not a complete formula for unity, because there were still many other steps to be taken to reach the goal.
Forgiveness was the principle of the bill. Whether this would materialise rested with parliament, Gen Sonthi said.
He rejected suggestions that he went to see Thaksin to take "an assignment" before formally proposing the bill.
Meanwhile, a Senate meeting yesterday debated the reconciliation bill.
Senator Somchai Sawaengkarn said the bill would undermine the credibility of the courts of justice. Several cases pending in the courts would be dismissed as a result of its passage and the judicial process thrown into disarray.
Senator Kamnoon Sitthisamarn said the legislative branch was taking an unprecedented and improper step in considering revoking court rulings.