Tennis great John Alexander says he’ll campaign like “never before” to win back his seat, after becoming  the latest federal politician caught up in the dual citizenship debacle.

Mr Alexander’s resignation from parliament is expected to be made official today after the Liberal MP discovered he was a British citizen.

Speaking with 2GB’s Alan Jones, he admitted it’s been it’s been a tough week, “The member must be of the belief  they are not a dual citizen. As we investigated every option I could no longer be sure of that belief. It defies common sense. There’s people with degrees and there’s people with degrees of common sense.”

Writs for the by-election are expected to be issued today for a poll to be held on December 16.

Mr Alexander must have his citizenship renunciation accepted before he can be pre-selected for the Sydney seat of Bennelong.

“I’ve been in contact with the High Commissioner to renounce my citizenship. That should happen within a few days.”

“We will campaign, if I’m fortunate to get the support of the party, as we’ve never campaigned before”.

2GB Breakfast host Alan Jones is backing his long-time friend to overcome the situation facing him and return to parliament.

“He’s a man of impeccable honour. He wasn’t forced to resign. Indeed I can say… he won’t say, he tried very significantly to get in touch with his leader [Malcolm Turnbull] but that was very, very difficult. The leader was too busy.”

“Well, we’ve found a leader here, he’s showing the leader of the party how to lead.”

Listen to the full interview below