One of the country’s two Ombudsmen has resigned and will leave the role two years before the end of his five-year term.

Professor Ron Paterson will leave the role on Thursday. He was appointed an Ombudsman in June 2013 for a five-year period.

Deputy Ombudsman Leo Donnelly will be appointed temporary Ombudsman for a 12-month period, which could be extended by another two years.

The change comes as the office attempts to clear a backlog of 650 investigations that have been pending for more than a year.

In December, Principal Family Court Judge Peter Boshier was appointed Chief Ombudsman.

At the time, he acknowledged the office had a reputation of being slow when deciding on complaints relating to Official Information Act requests, or complaints from people relating to public agencies.

His goal is to have all complaints resolved within a year.

Prior to his taking up the role of Ombudsman, Professor Paterson was a Professor of Law at the University of Auckland and New Zealand Health and Disability Commissioner from 2000-2010.