The Guardia Civil’s Unidad Central Operativa (UCO) has placed Juan Manuel Serrano, former president of Correos and former chief of staff to Pedro Sánchez, at the center of an investigation into alleged efforts to interfere with judicial proceedings involving the PSOE and the Spanish government. In a report submitted to investigating judge Santiago Pedraz at the Audiencia Nacional, investigators allege that Serrano was involved in a network seeking to destabilize cases that could affect the ruling party and its leadership.
Serrano was formally placed under investigation on 10 July 2026, after a police report identified alleged links to two strands of the Leire Díez case. One concerns alleged attempts to influence investigations affecting the PSOE; the other concerns suspected irregular commissions linked to public contracts, a line Serrano’s defence has called the “SEPI strand.” He is under investigation, not a convicted defendant.
The UCO report points to evidence concerning Serrano’s alleged involvement alongside Leire Díez, a former PSOE member. Santos Cerdán, the party’s former secretary of organization, is also named. Investigators are examining whether the group sought business advantages involving the Sociedad Estatal de Participaciones Industriales (SEPI) while pursuing efforts to protect political allies. The alleged SEPI strand includes a group referred to as Hirurok, involving Díez, former SEPI president Vicente Fernández and businessman Joseba Antxón Alonso, identified as a business associate of Cerdán.
Investigators are also examining Díez’s appointment at Correos, where she joined in November 2021 during Serrano’s tenure as president. UCO material reportedly describes the appointment as potentially strategic within the wider alleged public-contract scheme and says her placement was apparently discussed directly with Serrano. Separately, Anticorruption prosecutors allege that a contract connected to the rehabilitation and possible relocation of Mercasa’s headquarters included a fictitious overcharge of approximately €700,000. A public-company audit reportedly found that Servinabar 2000, a company linked to Cerdán, prepared a technical study before the formal contracting process began and breached internal rules.
The case has also brought scrutiny to communications cited in the police investigation. In a reported exchange dated 29 April 2026, Díez asked Serrano whether they would have to continue with what they had started the previous Friday. Serrano replied that, in principle, they would continue while watching how events developed. The file also reportedly includes messages in which Díez told Serrano about interviews with former police commissioner José Manuel Villarejo. Investigators are assessing the communications as part of the alleged judicial-interference strand.
On 27 May 2026, the UCO seized Serrano’s iPhone 15 Pro Max. In a filing dated 6 October, Anticorruption prosecutors Elisa Lamelas and Mar Scharfhausen opposed returning it, arguing that the device remained potentially relevant to the proceedings. Their filing responded to Serrano’s appeal against the seizure; the competent chamber of the Audiencia Nacional will decide the challenge. The prosecutors’ position keeps the phone within the investigation’s evidentiary scope while the court considers the appeal.
Judge Pedraz is also seeking information from the PSOE about the lawyers and law firms it retained between 2021 and 2025. The party has asked for more time, saying the campaign period has reduced its capacity to respond. The request is part of the broader inquiry into alleged attempts to influence judicial proceedings and suspected irregularities involving public contracts; the extension request itself does not establish wrongdoing. Cerdán, for his part, has criticized the breadth of the investigation, accusing the Audiencia Nacional of examining his entire life in search of offences.
The developments add to scrutiny of the PSOE’s internal workings and its connections to state-owned enterprises. The case has already led to formal charges against Díez and Cerdán, intensifying political pressure and raising questions about oversight within public institutions. The Audiencia Nacional is handling the investigation, which continues to examine communications and financial records. The case has drawn comparisons with other recent controversies involving SEPI and PSOE officials, including the dispute surrounding María Jesús Montero and Vicente Fernández, as detailed in a related report on the widening SEPI investigation: Montero distances herself from the SEPI affair as the probe expands.
SEPI is a state holding company that manages public stakes in Spanish enterprises. The Audiencia Nacional, Spain’s central criminal court, handles major criminal investigations, including complex cases involving alleged political corruption and financial misconduct. The inquiry puts the intersection of politics and public business under renewed scrutiny, with potential consequences for the PSOE and Spain’s public administration as investigators pursue the allegations.
