* More than 250 customers potentially affected
* Products used in cars, planes and industrial machinery
* Latest quality assurance scandal to hit Japan (Adds responses from companies, government)
TOKYO, Nov 24 (Reuters) - Mitsubishi Materials Corp saw its stock fall as much as 11 percent on Friday after it said three subsidiaries had falsified product data, marking the latest in a series of quality assurance scandals involving Japanese manufacturers.
Mitsubishi Materials said inspection data was falsified on parts used in aircraft, automobiles and industrial machinery, with potentially more than 250 customers affected.
The admission follows a spate of compliance failings at Japanese manufacturers including Kobe Steel Ltd, Nissan Motor Co Ltd and Subaru Co Ltd.
Minister of Economy, Trade and Industry Hiroshige Seko on Friday said the latest misconduct was "a betrayal of trust in Japanese manufacturing," pointing to the amount of time Mitsubishi Materials took to reveal the wrongdoing.
Mitsubishi Materials said data falsification at subsidiary Mitsubishi Cable Industries Ltd was discovered as far back as February.
The unit distorted data on around 20 percent of its rubber sealing products, used in aircraft and cars, for two-and-a-half years from April 2015. Of 229 potentially affected customers, 40 have been informed by the company.
Another subsidiary, Mitsubishi Shindoh Co Ltd, manipulated data for metal products, used in cars and electronics, as far back as October 2016. Around half of 29 potentially affected customers have been informed.
Mitsubishi Materials said it stopped shipping affected materials from the two units in October.
In both cases the company said it had not found any safety or legal problems.
A third subsidiary, Mitsubishi Aluminum Co Ltd, also shipped products which did not meet specification, with the safety of the affected products already confirmed with customers, the parent said.
Mitsubishi Materials said it did not know whether there would be any impact on its financial outlook and has set up a task force to look into the problems and to devise countermeasures to improve quality control.
With affected Mitsubishi Materials products used in defence equipment including aircraft engines, Japan's defence ministry is working to establish the impact of the wrongdoing but does not currently plan to stop using any equipment, Defence Minister Itsunori Onodera said on Friday.
The company reported to the transport ministry around midday today, a ministry spokesman said.
Mitsubishi Materials does not directly supply parts to Airbus SE, which has not yet identified any suppliers receiving products from the company, an Airbus spokesman said.
Other manufacturers such as Boeing Co, Toyota Motor Corp, Honda Motor Co Ltd, Mitsubishi Heavy Industries Ltd and Nissan said they were looking into the issue, company spokespeople confirmed.
The news comes after Kobe Steel, Japan's third-biggest steelmaker, admitted in October that workers had tampered with product specifications, forcing companies around the world to check the safety of their products.
Mitsubishi Materials plans to hold a news conference at 0630 GMT.
(Reporting by Sam Nussey; Additional reporting by Kentaro Hamada, Jamie Freed, Nobuhiro Kubo and Naomi Tajitsu; Editing by Stephen Coates and Christopher Cushing)