Each target will have a lead minister and a lead chief executive.
Mr Key did not indicate there would be any formal penalty imposed for failing to reach the target.
"I expect them to be held to account and they will be held to account through the New Zealand media and through the public and the public reporting of that.
"But in the end the biggest way we are held to account is called a general election."
Mr Key's plans for public accountability are taken from the recommendations of the Better Public Services Advisory Group.
The group also advises giving proven leaders in the public sector a greater say over budgeting, which at present is the domain of ministers.
And it wants the three central agencies, the State Services Commission, the Department of Prime Minister and Cabinet and Treasury to work more closely together.
The advisory group did not believe there was a need for a sharp reduction in the number of Government agencies.
Mr Key announced the merger of four existing ministries into one, the Ministry of Business, Innovation and Employment on July 1.
It will absorb the Ministry of Economic Development, the Department of Labour, the Ministry of Science and Innovation and the Department of Building and Housing.
It would have a staff of 3200 which was the same as the four agencies combined.
"In the end what's really important is that we are delivering the right results at the right cost to the taxpayer and I don't think we should stop doing things because they are challenging," Mr Key said.
Labour leader David Shearer said that after three-and-a-half years New Zealanders should expect Mr Key to be delivering some results, not just setting targets.
All New Zealanders want to see a reduction in people on welfare, the crime rate and assaults on children.
"Frankly this is just another list. It follows on from the six-point plan in 2010, the revised six-point plan in 2011 with 41 actions, and 2012's 120-point plan," he said.
"More lists and more bullet-pointed plans are simply not going to grow the New Zealand economy, create high value jobs and help Kiwis get ahead."