A Wall Street credit rating agency is warning that Illinois could face another debt downgrade if lawmakers adopt Gov. J.B. Pritzker's budget plan.

Fitch Ratings said in a news release Tuesday that the plan Pritzker presented last week "would not materially address the state's structural budget issues in the current fiscal year or the next." The warning comes four days after S&P Global Ratings panned the new Democratic governor's spending plan for the budget year that begins July 1, calling it "precariously" balanced.

Like S&P, Fitch took issue with Pritzker's plan to stretch out pension payments to lower short-term costs while extending the state's funding deadline by seven years. The administration says it's part of a multifaceted plan that also includes infusing cash into the severely underfunded retirement systems by selling state assets, issuing bonds and dedicating revenue from a proposed graduated-rate income tax plan.

Shifting the state from its current flat-rate income tax structure to one where higher earners pay higher rates would require voters to approve an amendment to the Illinois Constitution. That can't happen until November 2020 at the earliest.

In the meantime, Pritzker has proposed raising about $1.3 billion in new revenue through a series of taxes and fees -- including licensing fees from legalized sports betting and recreational marijuana -- to help close the state's estimated $3.2 billion deficit.

"This is not the work of just one year," Pritzker said last week in his budget address. "Real fiscal stability requires a long-term commitment to paying down debt, investing in critical infrastructure and stabilizing our pension system."

While some are optimistic the state will have an easier time adopting a budget now that Democrats control the governor's office and both the Illinois House and Senate, Fitch said single-party control "is not a panacea for Illinois."

"It also would not mean the end of the state's credit challenges, which have persisted regardless of the political make-up of the state government," the ratings agency said. "Illinois faces significant fiscal problems that will likely take multiple years to fully address, but the executive budget does not provide enough clarity on how the state will deal with them."

In a statement, Pritzker spokeswoman Jordan Abudayyeh, said that the alternative to the governor's approach "is doing more of the same: namely, raising taxes on the middle class.