Turkey's main opposition party launched a legal challenge at a top court Friday to last-minute changes to voting rules in the referendum that saw President Recep Tayyip Erdogan win expanded powers.
The 'Yes' side won 51.4 percent of the vote in last Sunday's referendum on creating an executive presidency, axing the role of prime minister from 2019.
But there was controversy after the Supreme Election Board (YSK) made a last-minute decision to accept ballot documents in envelopes without an official stamp, which the opposition argues opened the way for fraud.
The Republican People's Party's (CHP) lawyer Atilla Kart formally lodged the petition with the Council of State on Friday afternoon, telling reporters the move was not "just for the 'No' voters" but for the protection of all voters' legal rights.
The Council of State, set up during the Ottoman empire, is Turkey's highest administrative court.
Kart added there were also 'No' voters among the unstamped ballot envelopes the YSK allowed, describing the situation as "complete lawlessness".
Earlier, CHP deputy leader Bulent Tezcan said the party would open a case calling for the cancellation of the YSK's decision to allow the rule change.
Together with the third largest pro-Kurdish Peoples' Democratic Party (HDP) and another opposition party not in parliament, the CHP called for the referendum to be annulled this week.
On Wednesday, 10 members of the YSK decided against annulling the vote, while only one voted in favour.
Tezcan earlier urged the results not to be finalised until the case was concluded. The results are expected to be confirmed on April 27 or 28.
"Whether citizens said 'Yes' or 'No', we will continue our legal fight until the end to protect the rights of the 49 million citizens who voted," Tezcan said.
- 'Wasting time' -
Turkish Prime Minister Binali Yildirim responded by saying it was "not the democratic way to go to court, to make complaints to fix the people's decision".
Speaking to reporters in Ankara, Yildirim said the CHP and others had the right to challenge but "there was nothing we could say about using this".
Yildirim added: "The people have made their decision.... Disagreeing with the people's decision suggests not believing in democracy as much as necessary."
He described such efforts as "futile" and said there was "no point in wasting more of everyone's time".
Election monitors criticised the referendum process and the YSK's ruling on unsealed envelopes earlier this week.
Cezar Florin Preda of the joint mission of the OSCE Office for Democratic Institutions and Human Rights (ODIHR) and the Parliamentary Assembly of the Council of Europe (PACE) said the late changes in counting procedures "removed an important safeguard".
Kart said the CHP was evaluating whether one of the ways to challenge the vote included applying to the Constitutional Court or the European Court of Human Rights (ECHR).
"Right now, an application can be made to the Constitutional Court or ECHR," he said.
But Erdogan on Thursday mocked the CHP's suggestions that it could go to the two courts with requests to cancel the referendum.