NI21's John McCallister has resigned from the troubled political party he formed with Basil McCrea.
The deputy leader told the Belfast Telegraph he will remain in politics as an independent unionist MLA for south Down and will continue to present NI21 policies and agenda.
Northern Ireland's newest political party has been on the brink of collapse since a major public falling out between Mr McCallister and party leader Basil McCrea when Mr McCallister instigated an external investigation into allegations of inappropriate sexual activity against his former colleague.
Mr McCallister said his position as deputy leader, chief whip and member of NI21 had become untenable after the investigation by mediation firm Carecall was halted by the party.
The allegations - which Mr McCrea strongly denies - have now been referred to the Assembly’s Commissioner for Standards.
Mr McCallister said that had Mr McCrea stepped down as party leader while the investigation was ongoing he may have stayed within the party.
“I have written to the party chair to inform him that I have resigned as party deputy, chief whip and my membership of NI21.
He added: "With everything that has been going on within the party over the last few months, I have felt in a very difficult position. I felt my time shouldn't be spent fighting over issues within NI21 whenever I should be fighting for the issues that matter to the people of Northern Ireland."
Mr McCallister said he intends to stay an independent unionist MLA for south Down "to focus on continuing to be a good, active constituency representative".
He added that he will "still be out presenting the values and agenda that I wrote for NI21 about wanting to see a normal society, about wanting to see a government in opposition, wanting to see a tolerant, inclusive, pluralist pro union voice in the assembly."