Agbéyomé Kodjo made the accusation against President Faure Gnassingbé who has been in power since 2005 when he took over from his father.
The president’s office is quoted by AFP news agency as denying the accusation.
Provisional results indicate that Mr Gnassingbé, has won a fourth term.
Early today, the electoral commission said that Mr Gnassingbé had received 72% of the vote, compared with about 18% for Mr Kodjo. Mr Kodjo, former prime minister and head of the national assembly, also accused the authorities of ballot stuffing and getting people to cast multiple votes in Mr. Gnassingbé’s favor.