A Mexican presidential candidate has accused the country’s intelligence service of surveilling his campaign – part of a pattern of alleged espionage against opponents of President Enrique Peña Nieto and his embattled administration.

Ricardo Anaya, the likely candidate for a right-left coalition, posted a tweet on Tuesday showing him confronting a person following him in a Jeep. After an awkward handshake, the driver readily identified himself as working for Cisen, the Mexican intelligenceservice. He said he was following Anaya “so that there’s no problem”.

“Instead of pursuing criminals, they’re spying on opponents,” Anaya tweeted.

“This is what they’re spending state money on. That’s why we are the way we are,” he added, alluding to Mexico suffering its most murderous year on record in 2017.

The left-leaning poll-leader Andrés Manuel López Obrador has also said that he and his family have been spied upon. He has promised to disband Cisen if he wins the 1 July election.

The latest accusations come as Mexico prepares for a contentious presidential campaign. The ruling Institutional Revolutionary party has been bogged down by corruption scandals and the sedate style of its proposed candidate, the former finance minister José Antonio Meade, has failed to excite voters.

Anaya, a former congressman with the right-leaning National Action party, has placed second in most polls, though some on social media voiced suspicions he was trying to create publicity at a time when the rules require candidates to keep a low profile.

Accusations of espionage using sophisticated spying software surfaced against Peña Nieto’s government last year. Journalists, NGO workers and opposition politicians had their smartphones targeted, according to experts at the University of Toronto.

Cisen has a history of targeting political opponents. “What we were usually subject to were these strategic leaks of recorded conversations that put the person in a bad light,” said Federico Estévez, political science professor at the Autonomous Technological Institute of Mexico.

Cisen, he added, “has turned back into a political espionage centre”.

The interior minister, Alfonso Navarrete, rejected the allegations, saying Cisen personnel were simply “following public activities and events occurring in the country”.