The revised charter paves the way for elections of all Upper House members, and not partial appointment as imposed by the current constitution.
Ms Yingluck said she followed the legal procedure which requires the prime minister to seek a royal approval of the bill within 20 days after its passage in the final third reading.
A group of opposition MPs and 40 senators recently sought the Constitution Court’s injunction against the bill, saying the parliamentary amendment of the charter was a breach of Section 154 of the constitution.
Responding to the move, Ms Yingluck said the cabinet’s secretariat, the Council of State and related state agencies have considered the opposition and senatorial observations and concluded that the legal procedure (in passing the bill) was in accord with the constitution.
Jurin Laksanawisit, chief of opposition whip, warned Ms Yingluck of possible charges of the offence of negligence of duty if she insisted on submitting the bill for royal endorsement.
He said the amended charter, though passed in the final reading by Parliament, was pending the Constitution Court’s ruling after a petition by MPs and senators, and the prime minister’s insistence to forward it to His Majesty the King would be a violation of Section 157 of the constitution.
Parliament Speaker Somsak Kiatsuranond would also be charged with negligence of duty for his refusal to forward the opposition’s petition to the Constitution Court and his failure to inform the prime minister of the opposition’s move.
Parliament is collaborating with the government in ramming through the controversial bill, said Mr Jurin.