Conall McDevitt, a leading member of the SDLP, has resigned after a row over undeclared earnings.
Mr McDevitt failed to declare more than £6,000 he earned from a public relations company shortly after he was appointed as a Stormont Assembly member.
Mr McDevitt said he was quitting politics with immediate effect.
SDLP leader Alasdair McDonnell said he supported Mr McDevitt's decision to resign.
