The petitions had been filed by the main opposition Republican People’s Party (CHP), the Peoples’ Democratic Party (HDP) and the Patriotic Party.
Ten out of 11 board members voted against the appeals, the YSK said in a statement.
“The YSK meeting to discuss the applications for cancelling the referendum due to complete illegality, began today at 10.30 [0730GMT],” the statement said.
“The board voted separately on all three applications. Ten members voted against, one agreed and the applications were rejected by majority vote as of 17.30 [1430GMT].”
CHP Deputy Chairman Bulent Tezcan condemned the decision.
“This is a serious legitimacy crisis,” he told reporters in Ankara. “This is not only a problem about the No votes but an injustice against all citizens who cast their votes. Because, the Yes votes also became controversial through this decision.”
The CHP has led criticism of the result of Sunday’s referendum, particularly the YSK’s decision to include ballot papers unverified by the local electoral board in the count.
The party said it would not recognize the result and explore every avenue to overturn the result, including applying to the Constitutional Court and the European Court of Human Rights.
Voters went to the polls on Sunday to decide whether to approve changes to the country’s constitution that would usher in an executive presidency.
The unofficial results show the Yes campaign won with 51.41 percent, while No votes stood at 48.59 percent. Voter turnout was 85.46 percent.
The official results are due to be released at the beginning of May.