Nissan has admitted to falsifying emission tests data at plants in Japan, and said a full investigation has been launched.

Shares in the car maker dropped almost 5 per cent after the group released a statement outlining misconduct in exhaust gas measurement within final vehicle inspections in Japan.

The group said it had uncovered evidence that exhaust emissions and fuel economy tests were carried out in a way that deviated from the prescribed testing environment, and that inspection reports were created based on altered measurement values.

“This issue came to light during the course of voluntary checks conducted by Nissan,” the firm said.

“As a companywide exercise, Nissan will continue to carry out comprehensive checks of frameworks, organisations and processes related to regulatory compliance.

“Strict adherence to compliance is a top priority for Nissan’s management, and if issues are discovered, appropriate measures will be taken. Nissan is committed to promoting and enforcing compliance and awareness thereof in all operational areas.”

Nissan said it had reported the current facts and investigation results to the Japanese Ministry of Land, Infrastructure, Transport and Tourism.

The company said: “Nissan understands and regrets the concern and inconvenience caused to stakeholders as a result of its kanken [final vehicle inspection process] issues last year. Proactive initiatives to prevent recurrence of such issues have led to the discovery of this misconduct, for which the company is regretful.

“A full and comprehensive investigation of the facts outlined above, including the causes and background of the misconduct, is underway.”

Japanese law firm Nishimura and Asahi has been brought in to carry out the investigation.

The group confirmed, “following re-verification of reliable log data”, that all vehicles produced, except GT-R, conform to Japanese safety standards.

The news has echoes of the emissions scandal that engulfed Nissan’s rival, Volkswagen, in 2015, when it was revealed that VW had fitted so-called “defeat” software designed to fool emissions tests on millions of its diesel cars.

There is no evidence that the misconduct at Nissan was as widespread as it was at VW; several of the German car maker’s top figures were implicated, with a number of senior staff arrested over the scandal.