One of Venezuela’s top election officials, in a declaration sure to jolt the crisis-weary nation, said in an interview that he had no proof that Venezuela’s authoritarian president won last month’s election.

Since the July 28 vote, governments around the world have expressed skepticism, and even outright disbelief, over President Nicolás Maduro’s claim to victory. But the statement by Juan Carlos Delpino — a member of the government body that announced Mr. Maduro’s win — represents the first major criticism from inside the electoral system.

Speaking on the record to a reporter for the first time since the vote, Mr. Delpino said he “had not received any evidence” that Mr. Maduro actually won a majority of the vote.

Neither the electoral body nor Mr. Maduro has released tallies to support assertions that the president won re-election, while the opposition has published receipts from thousands of voting machines that show its candidate, Edmundo González, won an overwhelming majority.

In declaring Mr. Maduro the winner without evidence, the country’s election body “failed the country,” Mr. Delpino said. “I am ashamed, and I ask the Venezuelan people for forgiveness. Because the entire plan that was woven — to hold elections accepted by all — was not achieved.”

Mr. Delpino, a lawyer and one of two opposition-aligned members of Venezuela’s electoral council, spoke from hiding, afraid of government backlash. In recent weeks Mr. Maduro’s security forces have rounded up anyone who appears to doubt his claim to another six years in power, and many Venezuelans are fearful that his forces are crossing borders to go after enemies.