The Opposition has tabled a motion in parliament calling for a vote to summon Konrad Mizzi to appear before the public accounts committee.

It is urging the House to take a vote tonight before the prime minister's budget speech.

Mizzi has already twice turned down requests by the PAC to appear before it to face questions on the Electrogas power station project.

"The ball is in the government's court now. Now is the time for government MPs to go from words to actions," committee chair and Nationalist MP Beppe Fenech Adami told a press conference. 

"We have asked Konrad Mizzi to answer questions twice, and he refused both times. This is unprecedented and unacceptable."

Mizzi, a former energy minister, is no longer a Labour MP and sits in the House as an independent. 

He has cited parliamentary rules to justify his absence, arguing that MPs have every right to refuse to appear before parliamentary committees.

Fenech Adami called on the prime minister to rally the government parliamentary group in favour of the opposition's motion.

"If Robert Abela refuses, then he too will be defending the corrupt Electrogas deal," Fenech Adami said.

"Konrad Mizzi was the brains behind the Electrogas deal," MP Karol Aquilina added.

"He can provide all the answers to our questions."

He recalled that last week he had asked Finance Minister Clyde Caruana whether Mizzi should appear before the PAC and Caruana said he should respect any invitation made to him by parliament.

Konrad Mizzi was expelled from Labour's parliamentary group on June 23 last year but he defied Robert Abela by refusing to tender his resignation from the House, saying that he saw no reason to step down.

Within hours of that statement, Abela had called a joint meeting of the party's executive and parliamentary group, which took a vote and expelled him from the group.