Conrad cited the Congressional Office Budget report that said the plan passed by Congress on Tuesday added $4 trillion to the deficit over the next decade.
Conrad called on his colleagues to keep fighting for deficit reduction in the next Congress, which starts Thursday.
Conrad called for reform on entitlements and ending tax expenditures as a balanced way to reduce the deficit.
“My greatest regret in leaving here is that we have not been able to fashion a grand bargain deal before I have left,” Conrad said.
Conrad is retiring after years of service on the Senate Budget Committee.