President Michel Temer on Thursday defiantly said he will not resign after the Supreme Court authorized an investigation into allegations he condoned bribes to a potential witness in a major corruption probe.

The investigation raised the possibility Brazil could see a second president fall in less than a year and sent Brazilian financial markets tumbling on doubts Congress will pass Temer's ambitious austerity agenda.

In a terse five-minute speech broadcast nationwide, Temer said he has done nothing wrong, that his presidency is helping turn around Brazil's stalled economy and he welcomes an investigation so that he can prove his innocence.