A CO Tyrone councillor who has quit Sinn Féin has accused the party of "nepotism and misogyny".
Sorcha McAnespy now intends to run as an independent candidate in next month's assembly elections.
The former vice-chair of Omagh District Council claimed she had been "marginalised" within Sinn Féin in favour of newer members with less experience.
Ms McAnespy (36) said she raised her concerns with the party but did not feel she received adequate support.
"There's too much nepotism and misogyny present in the party locally. It's jobs for the boys. It is not open and transparent," she claimed.
"Sinn Féin needs to support their elected representatives. They need to find mechanisms to support people who feel this way."
Ms McAnespy, who revealed her decision to quit the party in the Ulster Herald on Thursday, gained the most first-preference votes for the party in the Omagh ward in the 2014 council elections.
But the mother-of-three yesterday said she has been feeling discontented for several years, claiming she was being "undermined".
"I just felt you were being restricted whatever way you went. It wasn't nice," she said.
She added: "I was hoping things would get better. I was hoping that I would be able to find another way around this."
Ms McAnespy said she had "no beef" with the main party and no disagreement generally with its policies, but her difficulties were at a more local level.
An engineer before she was first elected in 2011, the councillor said she hopes to run a positive assembly campaign.
"I am very passionate about my county. Politics is local, and we need to keep a strong voice," she said.
The dispute emerged just months after Sinn Féin faced problems over the selection of assembly candidates in the neighbouring constituency of Fermanagh and South Tyrone.
Former MP Michelle Gildernew lost out to Phil Flanagan when the party held a re-run of its contest to choose three candidates.
But Ms Gildernew was re-selected after Sinn Féin chose to hold another vote to decide on a fourth candidate.
Political commentator Chris Donnelly said on Thursday night that Sinn Féin is likely to retain its three MLA seats in West Tyrone despite Ms McAnespy's candidacy.
"This one is unlike Fermanagh and South Tyrone in that I can't see this contributing towards a loss," he said.
But he added: "It is another sign that Sinn Féin in the north is beginning to move towards a normal political party where there would be this type of fall-out.
"That will bring challenges to Sinn Féin at a leadership level. They like to maintain internal discipline."
A Sinn Féin spokesman said: "We are disappointed at Sorcha McAnespey's decision to leave Sinn Féin. We thank her for her service.
"Sinn Féin's team of candidates for West Tyrone in the upcoming assembly election were selected by the delegates of the party at an open and democratic selection convention."
