Mexican prosecutors say they have opened a criminal investigation of a leader of Mexico's Green Party for allegedly violating electoral laws in June's midterm elections.

Prosecutors did not identify the official, but a statement posted on the Twitter account of Green Party leader Arturo Escobar says he has resigned his post as a government undersecretary for crime prevention. A federal official, who agreed to discuss the matter only if not quoted by name, confirmed that Escobar is the subject of the investigation.

The Green Party has issued a statement denying Escobar had done anything wrong.

The party was accused of exceeding spending limits before the elections and offering gifts or gift cards during the campaign. Those are prohibited by law.