The NACC also announced Tuesday it would make public its finding on the role of caretaker Prime Minister Yingluck Shinawatra in the rice scandal on either May 8 or 13.
It rejected on Tuesday a request by the prime minister's legal team to call seven more witnesses in the case.
In the senate matter, the NACC said there is a case that the 32 senators involved misused their authority and violated Section 291 (1) of the constitution when they tried to amend the constitution to have all senators come from elections.
Under the 2010 charter, 77 of the 150 senators are elected. The rest are appointed by a committee consisting of chairmen of the Constitutional Court, the Election Commission, ombudsmen, the NACC and the State Audit Commission, as well as one judge each from the Supreme Court and the Supreme Administrative Court.
Technically, the NACC decision means almost nothing - for the moment. The finding that there might be a legal case means the senators have to step down from their position, but in fact they already did that last month, to make way for new senators elected in the March 30 polls.
The real effect of the NACC decision is that the 36 ex-senators will have to face the malfeasance charges at the Supreme Court’s Criminal Division for Persons Holding Political Positions. Any ex-senator convicted there will be automatically banned from politics for five years.
The NACC's finding of a prima facie case against the ex-senators also indicates the anti-graft body might proceed with similar charges against MPs who also voted for the draft amendment to the 2007 charter.
Like the senators, the MPs reached the end of their term when Prime Minister Yingluck Shinawatra dissolved the House last Dec 9. Just as in the case of the ex-senators, the real blow for them is a potential ban from politicsใ
Many of the MPs facing possible NACC action are believed by political analysts to be likely leaders of a Pheu Thai Party campaign when a new election is called, with many also being groomed for leadership roles.
Legal experts said Tuesday the NACC appeared to focus on Section 6 of the draft amendment to the constitution. It would have allowed senators whose terms had expired to run again for another term, without a break.
All senators charged by the NACC had voted in favour of this section of the amendment, which was eventually ruled unlawful by the Constitutional Court.