A SENIOR Labor frontbencher has questioned whether a Nationals Senator excuse for being elected while holding dual citizenship stacks up.

Matt Canavan became the third senator in as many weeks to be caught up by section 44 of the constitution which permits members of parliament to be citizens of Australia and renounce any other citizenships.

Blaming his mum, the Queensland Senator yesterday announced he had only just found out he had been bestowed Italian citizenship without his knowledge or consent.

While he was born in Australia and has never been to Italy, Senator Canavan said his mother registered herself and members of her family as an “Italian resident abroad” — a form of citizenship — with the Italian consulate in Brisbane in 2006. He was 25 at the time.

He told a press conference yesterday: “Until last week, I had no suspicion that I could possibly be an Italian citizen.”

But Labor MP Tony Burke wasn’t buying it, and questioned the validity of his excuse.

“I don’t fully understand the explanation he’s given, I’ve gotta say,” the manager of Oppositon business told ABC’s Lateline.

“I’ve tried to piece together how it is that something like this, or why on earth something like this, would be kept secret from him.

“But that’s the version of events that he’s provided publicly and you’ve gotta presume that’ll be tested before the courts.”

Questions have been raised over how as an adult the former Minister had the citizenship process completed on his behalf, without having any interviews or signing forms.

Deputy Prime Minister Barnaby Joyce, who is acting as Minister for Resources and Northern Australia while Senator Canavan steps aside, this morning said his colleague “had not completed any forms” in relation to his Italian citizenship.

“In fact I think they’ve found the forms, and they’re unsigned,” he said.

The Coalition government is seeking legal advice on the matter, but its preliminary view is that Senator Canavan is not in breach of section 44, believing his case falls into “unique” circumstances.

Senator Canavan, who was considered a rising star of the Coalition after being promoted to cabinet last year after just two years in parliament, has not resigned from the upper house, but has stepped down from the ministry until the matter is resolved.

The High Court will decide his political future.

The embarrassing blunder comes after Prime Minister Malcolm Turnbull admonished the Greens for being “sloppy” and showing extraordinary negligence” when both the party’s deputy leaders, Scott Ludlum and Larissa Waters, were forced to exit the Senate after discovering they held dual citizenship.

Before discovering one of his own ministers was a citizen of Italy, Mr Turnbull said the mistakes showed “incredible sloppiness” by the Greens.

“When you nominate for parliament there is actually a question, you’ve got to address that question, tick the box and say you’re not a citizen of that country,” he said. “It’s extraordinary negligence on their part.”

Mr Burke told Lateline his party wouldn’t be making similar, “arrogant” comments.

“I think Malcolm Turnbull would be regretting those words right now,” he said.

Greens leader Richard Di Natale this morning told ABC radio he believed Senator Canavan should resign the Senate.

“Ignorance is no excuse, that was very clearly communicated to us,” he said.

“If you’re a real Italian, you never blame your mum for anything, so that might be his only defence.”