Ulster Unionist David McNarry had a stark message for his old party as he formally announced his decision to join the UK Independence Party.
Asked if he had mixed feelings about the move, having been in the UUP most of his adult life before an acrimonious fall-out, the Strangford Assembly Member said: "I am a politician, I am a professional politician and as far as I am concerned I am on the way up. I am not associated with anybody or anything that's in decline, and you best understand that. I'm on the way up."
Mr McNarry said any of his erstwhile colleagues in the UUP would be welcome in Ukip if they decided to jump ship.
He added: "I have not defected from anyone, I have willingly joined — the choice was mine."
Ukip leader Nigel Farage was at Parliament Buildings in Stormont, Belfast, with Mr McNarry to welcome the party's first Assembly Member into its ranks.
He said the development was proof that Ukip was a "truly, genuinely national" party, accusing other political parties of ignoring Northern Ireland.
"I think the fact the Westminster parties have completely given up on Northern Irish politics - completely given up - and the fact that we are now here today, we are sending a very big signal: we are a Unionist party, we are a Unionist party that wants to be involved in all the different corners of the United Kingdom," he said.
Mr Farage said Ukip had big plans for Northern Ireland and confirmed the party would stand in the region in European election in 2014.
"The ambition in 2014 is to come first (in the poll) across England, Scotland, Wales and Northern Ireland," he said.
Mr McNarry (64) fell out with the leadership of the Ulster Unionists in January after giving a press interview in which he talked up the prospect of the UUP joining forces with its main rival, the Democratic Unionists.
Disciplinary action by then-leader Tom Elliott prompted the MLA to resign from the party's Assembly grouping. He was subsequently expelled from the party outright.
The UUP has continued to be troubled with internal spats since Mr McNarry's departure. The latest saw new leader Mike Nesbitt sack his Assembly team's deputy leader John McCallister after interpreting comments he made in a speech as a criticism of his stewardship.
Mr McNarry insisted his decision to bring a fourth Unionist party - along with the UUP, DUP and Traditional Unionist Voice (TUV) - into the Assembly chamber did not run contrary to his belief in Unionist unity.
"I am a supporter of Unionist unity, you will know very well how some people took offence at that," he said.
"Insofar as Ukip's involvement, Ukip are a Unionist party and I have spoken to Nigel and Paul (Nutall, deputy leader) and we will play a full role in that.
"The key to Ukip's involvement in it is that Ukip are the only Unionist party with a national agenda."
PA