Gov. Peter Shumlin has abandoned his plan to institute a single-payer health system in Vermont.

The shocking policy reversal comes just six weeks after an election in which Shumlin had vowed, in unequivocal terms, to make Vermont the first state in the country with a publicly financed health care system.

But he said he learned late last week how much and what kinds of taxes would be required to pay for it. Faced with that information, Shumlin said Thursday, he opted to drop what has long been the central plank of his political platform.

“In my judgment, now is not the right time to ask our Legislature to take the step of passing a financial plan for Green Mountain Health Care,” Shumlin said.

Shumlin delivered the news at a mid-afternoon press conference in Montpelier, where supporters and opponents of single-payer had gathered for what administration officials promised would be a major announcement.

Shumlin said recent projections show that Vermont would need to raise far more than he initially envisioned to replace private health insurance premiums with public revenues. The program, he said, would have required a payroll tax of 11.5 percent, and a sliding-scale income tax that would have topped out at 9.5 percent.

“The bottom line is as we completed the financing modeling in the last several days, it became clear that risk of economic shock is too high at this time to offer a plan that I can responsibly support for passage in the Legislature,” Shumlin said.