The Carter Center said it was unable to verify the results of Venezuela’s presidential election, blaming authorities for a “complete lack of transparency” in declaring Nicolas Maduro the winner without providing any individual polling tallies.

The statement Tuesday night by the Atlanta-based group is perhaps the harshest rebuke yet of Venezuela’s chaotic election process because it comes from one of just a handful of outside groups invited by the Maduro government to observe the vote.

A renowned NGO that was invited by Venezuelan officials to monitor Sunday's presidential poll has said the election "cannot be considered democratic".

The US-based Carter Center deployed 17 experts and observers to Venezuela after being asked to monitor the election by the National Electoral Council (CNE).

On Monday, the CNE - which is dominated by government allies - declared President Nicolás Maduro the winner, but the result has been disputed by the opposition which says voting tallies show its candidate, Edmundo González, has won by a wide margin.

Sen. Rick Scott, R-Fla., is calling on the Biden-Harris administration to recognize Edmundo González as the "legitimate president-elect of Venezuela" after his conversation with Venezuelan opposition leader María Corina Machado.

According to Scott's office, since the election in Venezuela took place, the senator contacted the White House "repeatedly to schedule a call with President Biden."

The Organization of American States (OAS) is scheduled to hold a meeting on Wednesday on the results of the Venezuelan presidential election.