Following a meeting last night NZ First's board confirmed Mr Horan's membership of the party had ended.
Mr Horan was expelled from the NZ First caucus a week earlier amid allegations he took money from his dying mother's bank account to gamble.
On his way into Parliament this afternoon Mr Horan said he found out about the board's decision only from the media this morning. He said he had suffered a similar fate to that of former Labour Party MP Chris Carter who was expelled from his party.
In that case, unlike NZ First last night, Labour followed "due process'' by giving Mr Carter the opportunity to defend himself.
During Mr Peter's questioning of Prime Minister John Key about a deal to allow China Southern Airlines' frequent flyers easier visa requirements when visiting New Zealand, Mr Horan seized an opportunity to ask a supplementary question.
"Does the Prime Minister agree that natural justice and due process are relevant in the administration of the Immigration Act?'' he asked.
Picking up on Mr Horan's line, Mr Key said they were relevant "and I think it's important to be consistent when one's applying that''.
"I know that selection of people when they come to New Zealand is difficult but when there's 171,000 a year that's challenging, but when it's one of eight you'd think you'd get it right'' Mr Key said to laughter from MPs across the House.
Mr Horan was one of eight NZ First MPs including Mr Peters elected to Parliament last year.
The exchange prompted Mr Horan's former caucus colleague Richard Prosser to tweet a suggestion that Mr Horan's question had been written for him by National.
