Ankara: A top Turkish court Tuesday rejected an opposition legal challenge to last-minute voting rule changes in the referendum over handing President Recep Tayyip Erdogan greater powers.

The opposition Republican People’s Party (CHP) has repeatedly criticised the decision by the country’s top election authority to accept ballot documents in envelopes without an official stamp.

The party formally lodged on Friday a petition with the Council of State, Turkey’s highest administrative court, after the ‘Yes’ side won 51.4 per cent of the vote in the April 16 referendum.

The opposition, which argues that the decision by the Supreme Election Board (YSK) on the envelopes opened the way for fraud, launched a failed bid to annul the referendum last week.

The CHP said the decision by the election board was an “administrative” move.

However, the court rejected its challenge by a majority vote (four against and one in favour), saying it could not rule on the YSK’s move because it was “not an administrative procedure”, state-run news agency Anadolu reported.

Turkish Justice Minister Bekir Bozdag said on Saturday that decisions made by the YSK could not be challenged in the Constitutional Court nor in the Council of State.

Levent Gok, CHP’s parliamentary group leader, immediately hit back, accusing Bozdag of giving “instructions” to the judges before they had made a decision.

With the constitutional changes approved by voters, Turkey will implement an executive presidency from November 2019, axing the role of prime minister and empowering the president to appoint ministers.

An independent citizens’ organisation called “No and Beyond” which compiled information about irregularities encountered on the day of the vote claimed the referendum was “invalid on all kinds of legal grounds.”

“It is the cornerstone of democracy in our country and the right of every citizen to trust that the elections and public votes are safe from shady practices,” the group’s report published on Tuesday said.

“It is clear that this right cannot be established,” the report said.

Formed only two months ago, No and Beyond with close to 15,000 volunteers was at polling stations across Turkey.

In one example of 7,448 ballot boxes, the group said it had observed that over 2,397 contained more votes than the registered number of voters. The sum of the votes found in these ballot boxes was 1.67 million and 60.7 per cent of these votes were ‘Yes’.

Damla Atalay, a lawyer from the group, said the referendum must be repeated.

“But even if it is annulled, we have second thoughts if any second vote would be in compliance with the law,” she told AFP in Istanbul.

Atalay said most of the irregularities spotted by the group took place in the east and the southeast of Turkey.