The Alliance Party's deputy leader is to step down and will not stand in the next Assembly election.
Eileen Bell said the decision was primarily for personal reasons
Eileen Bell denied that a recent split within the party over gay civil partnerships was one of the main reasons for her decision.
The North Down MLA said it was mostly for personal reasons but she admitted that the row had been difficult.
"It has stressed me very much, because to me, Alliance is the party of equality and human rights," she said.
Mrs Bell said she hoped the party could work through these issues.
"On a personal level, I would like to get a life. I've spent over 30 years in politics and peace work," she added.
Last month, party chairman Trevor Lunn resigned, claiming he was the victim of a campaign by Alliance colleagues over his opposition to gay unions.
The Lisburn councillor opposed the use of the council's wedding room for civil partnerships.
The Civil Partnership Act creates a new legal relationship
Alliance backs civil partnerships, but its three Lisburn councillors disagree.
Alliance assembly member Seamus Close proposed a motion preventing the council's wedding room being used for same-sex unions.
However, the council overturned its policy regarding gay and lesbian unions.
The council had banned the use of its wedding room for same-sex civil partnership registrations, prompting gay activists to threaten legal action.
However, after consulting lawyers, a council committee decided the ban should be lifted.
The Civil Partnership Act creates a new legal relationship, which two people of the same-sex can form by signing a document.
It provides same sex couples with parity of treatment in a wide range of legal matters with those opposite-sex couples who enter into a civil marriage.