The parliamentary poll was much delayed and fraught with tensions.
President Alpha Conde's ruling party in Guinea took just under half of the seats in last month's parliamentary poll, electoral officials have said.
They said the Rally of the Guinean People (RPG) secured 53 seats in the 114-member parliament.
The main opposition party had 37 seats, while the rest went to smaller parties. The opposition said it would not recognise the result of the poll, which international observers said was marred by "irregularities".
President Alpha Conde narrowly won elections in 2010
Opposition spokesman Sydia Toure said the announced result of the 28 September election did not reflect "the people's vote". Earlier, the observers said that "breaches and irregularities were observed in a certain number of constituencies, preventing a significant number of votes from being taken into account".
The monitors included representatives from the UN, EU, West African block Ecowas and US and French diplomats.
The election in the west African nation is intended to replace a transitional parliament that has run the nation since military rule ended in 2010.
The run-up to the election was hit by violence, as well as ethnic and religious tension. It has been much delayed and was supposed to be held six months after the 2010 presidential elections, which Mr Conde narrowly won.