The election is expected to return President Emomali Rakhmon to office
Voting in Tajikistan's elections on Sunday was marred by widespread fraud, international monitors have said.
The Organisation for Security and Co-operation in Europe (OSCE) said the polls had "failed on many basic democratic standards".
It said there was evidence of ballot stuffing and proxy voting and media coverage of campaigning was minimal.
Early results give President Emomali Rakhmon's party, which dismissed the accusations, more than 70% of votes.
Mr Rakhmon has been in office for the past two decades and his People's Democratic Party holds virtually all seats in parliament.
OSCE co-ordinator Pia Christmas-Moeller said she was pleased by the "generally good atmosphere" on election day.
But she said she was "even more disappointed that these elections failed on many basic democratic standards".
The observers from OSCE and the European Parliament said there had been "serious irregularities" on polling day, including a high prevalence of family and proxy voting and cases of ballot box stuffing.
"Such serious irregularities weaken genuine democratic progress," said Ms Christmas-Moeller.
"There is still a long way to go, and hopefully the new parliament will take up this challenge."
Tajikistan's main opposition party, the Islamic Revival Party, also criticised the poll.
"The past elections in Tajikistan had nothing to do with democracy," Khikmatullo Saifullozoda, one of the party's leaders, was quoted by Reuters as saying.
The Tajikistan Election Commission said early results gave the People's Democratic Party some 71% of the vote.
The party earlier said there had been minor violations to the poll which would not affect the will of the Tajik people.