The Istanbul Chief Public Prosecutor’s Office on Wednesday formally called on the Court of Cassation to take legal action against the main opposition Republican People’s Party (CHP), citing evidence of election manipulation, illegal financing and breaches of data protection laws.

The letter sent by the office is vital in the investigation into the alleged criminal network of former Istanbul Mayor Ekrem Imamoğlu and senior party officials. Imamoğlu was arrested in March and has been in custody ever since.

According to the statement issued by the prosecutor’s office, the inquiry uncovered attempts “to manipulate elections, which are the indispensable elements of democratic political life,” and urged action under Articles 68 and 69 of the Turkish Constitution as well as Law No. 2820 on Political Parties. Prosecutors argue that the findings reveal systematic violations of constitutional boundaries that safeguard democratic processes.

Besides the letter sent to the court of cassation, the public prosecutor’s office on Tuesday released a nearly 4,000-page indictment on the network and Imamoğlu, in which the charges would carry a prison sentence of up to 2,430 years for the jailed mayor. Imamoğlu is separately facing charges of espionage.

The case is based on an extensive indictment prepared against 407 suspects, of whom 105 remain in detention. The charges stem from a complex web of alleged financial misconduct, data manipulation and municipal corruption that investigators say was used to benefit the CHP’s political activities. The CHP, meanwhile, rejects all allegations, while the ruling Justice and Development Party (AK Party) advocates that the proceedings are totally judicial rather than politically motivated.

“This case is not legal; it is entirely political. Its purpose is to stop the CHP, which came first in the last (local) elections and to block its presidential candidate,” CHP Chair Özgur Özel wrote on X.

The investigation gained national attention after the release of widely circulated “money-counting videos” that appeared to show CHP officials handling large sums of cash inside the party’s Istanbul provincial headquarters. Following these revelations, prosecutors launched a probe into whether the funds originated from illicit sources linked to public tenders and municipal contracts under CHP-run local administrations.

According to the indictment, incomes from these illegal operations were funneled through intermediaries and ultimately used to purchase the CHP’s Istanbul provincial headquarters building in 2019. Investigators allege that multiple municipalities governed by the CHP, including Beşiktaş, Şişli, Beylikdüzü, Ataşehir, Kartal and Maltepe, were involved in the transfer of unregistered cash used to finance the property.

Witnesses who spoke under the effective remorse provisions claimed that Imamoğlu personally oversaw the transaction, while senior party figures Fatih Keleş and Mustafa Can Poyraz were seen in the money-counting footage managing the cash. Prosecutors said that these funds were obtained through a network of bribery, coercion and money laundering connected to municipal contracts and political influence.

Data breach

The indictment also highlights findings from the National Cyber Incident Response Center (USOM), which discovered that the “Istanbul Senin” mobile app, developed by the Istanbul Metropolitan Municipality (IBB), unlawfully transmitted the personal data of 4.7 million users to servers located in the United States and Germany.

The data, prosecutors said, included sensitive user information such as location details, activity logs and demographic identifiers, transferred without permission in breach of the Personal Data Protection Law (KVKK).

A separate investigation into the “IBB Hanem” system revealed that the personal data of more than 11.3 million citizens, including ID numbers, residential addresses and ballot information, was emailed to a private company in November 2023. Authorities said these transfers lacked legal authorization and represented a direct breach of both domestic privacy regulations and international cybersecurity protocols.

Prosecutors further noted that the Supreme Election Council (YSK) had provided voter lists exclusively for election monitoring purposes, but that these lists were shared with unauthorized individuals outside the CHP’s official teams.

The data was allegedly analyzed using psychographic profiling methods to target specific voter groups and influence election behavior.

“Such acts constitute interference with the free will of citizens and endanger the democratic order of the state,” the statement said.

“The CHP has financed political operations and acquired property through criminal proceeds. These actions contradict democratic principles, the transparency of political life, and the rule of law,” it added.

Prosecutors underlined that the claims are not limited to individual misconduct but reflect an organized effort to create financial mechanisms that could alter electoral outcomes.

‘CHP closure disinformation’

The public prosecutor’s office, meanwhile, refuted claims that the CHP would be shut down.

In a statement released by the Chief Public Prosecutor’s Office, it was underlined that disinformation-oriented news was seen in some social and visual media publications, claiming that the indictment announced to the public on Tuesday and the letter written to the Supreme Court Chief Public Prosecutor’s Office demanded the closure of the CHP.

“Our letter only constitutes a notification due to legal obligation to the Supreme Court of Appeals on some financial irregularities of the mentioned party.”