Turkey’s PM Binali Yildirim has called on the country’s opposition to respect the outcome of the April 16 referendum. He made his comments as main Turkish opposition party, the Republican People's Party (CHP), said it is to formally apply on April 18 to the Supreme Election Board (YSK) for the annulment of the hotly contested referendum on expanding the powers of President Recep Tayyip Erdogan.

Erdogan and the ruling Justice and Development Party (AKP) claim the poll resulted in a 51.41% victory for those saying the country should switch away from a parliamentary system in favour of an executive presidency.

“Rumours of irregularities in the referendum are a vain effort to cast doubt on the result. The people's will has been reflected at the ballot box, and the debate is over,” Yildirim said on April 18, Reuters reported. “Everyone should respect the outcome, especially the main opposition,” the PM added.

The pugnacious Erdogan, who was congratulated on his victory by US President Donald Trump on April 18, made stronger comments in the face of complaints about the fairness of the referendum, telling international election monitors: “Know your place.”

However, with academics pinpointing apparent irregularities in the declared voting patterns, Turkey’s bar association stepped into the row, saying the last-minute decision by Turkey's electoral board YSK to allow unstamped ballots in the referendum was clearly against the law.

The move had prevented proper records being kept and could have affected the results, the Union of Turkish Bar Associations (TBB) - known as a body opposed to the current Ankara government - said, adding in a statement: "With this illegal decision, ballot box councils [namely, officials at polling stations] were misled into believing that the use of unstamped ballots was appropriate."

The TBB also claimed that the YSK decision led to irregularities and stopped the keeping of records that could uncover irregularities.

Kemalist and social democratic opposition party CHP said it had received complaints from many regions that people had been unable to vote in privacy and added that some ballots were counted in secret, the party’s deputy chairman Bulent Tezcan said on April 17.

It also decried the electoral board’s decision to accept unstamped ballots. However, the CHP has not shared with the public any evidence backing its claims that there were referendum irregularities. It has instead relied on its main argument that the decision to accept unstamped ballots was unlawful.

The European Commission on April 18 said alleged irregularities in the referendum vote must be investigated. “We call on the Turkish authorities to consider the next steps very carefully and to seek the broadest possible national consensus in the follow-up to the referendum. We also call on the authorities to launch a transparent investigation into these alleged irregularities,” Commission spokesman Margaritis Schinas told a regular press briefing.

The Organisation for Security and Co-Operation in Europe (OSCE) has argued that the constitutional referendum was fought on an uneven playing field.

On a related note, EU foreign policy chief Federica Mogherini said on April 18 that “we will discuss the outcome of the vote and the future of our relations with Turkey at the informal gathering of foreign ministers from the 28 EU member states, which I will chair next week in Malta”.