Mr Spencer will be appointed as the acting governor of the Reserve Bank for six months, following the departure of governor Graeme Wheeler on September 26, three days after the general election.
Mr Joyce said Mr Spencer and he had agreed there would be no change to the existing policy targets agreement (PTA) for the period he would be acting governor.
Under the existing agreement, the Reserve Bank was required to keep future consumer price index inflation between 1% and 3% on average over the medium term.
Mr Wheeler failed to meet that target for eight quarters until the fourth quarter last year. Inflation undershot the target starting in December 2014, against a backdrop of weak global inflation and low oil prices.
However, Mr Joyce said the existing PTA had served New Zealand well and there were benefits in maintaining consistency in the agreement.
''The renewed agreement will maintain continuity and stability in the monetary policy target over the election period and during the period of a new governor.''
