CHENNAI, Feb 16 (Reuters) - Hundreds of workers at a manufacturing plant of Apple supplier Flex in India's Tamil Nadu state staged a one-day strike on Friday, demanding higher wages and the recognition of a union.

Many electronics manufacturers in India, including Foxconn and Pegatron, lack a union, while automobile factories have higher levels of organising, according to labour welfare workers.

At Flex, unhappy over wages and policies, including tour allowances and medical leaves, all permanent workers, about 750, joined the Centre of Indian Trade Union, said union secretary E. Muthukumar.

He added Flex, which makes chargers for Apple, was unwilling to recognise the union at the plant, which employs roughly 4,000 people, including contractors, who did not join the strike.

"As house rents, education fees and other expenses have increased, it is not possible to sustain a livelihood with the current salary," the union had informed Flex in a letter reviewed by Reuters.

The workers requested wage raises for the next three years but could not reach an amicable resolution, according to the letter.

Flex did not respond to requests for comment.

Workers will return to the factory for the third and final shift, Muthukumar said, adding the union will decide on the next steps depending on the outcome of future negotiations.

As of March, Flex, which also manufactures products for Apple in the U.S. and China, employed nearly 172,000 people globally, including contractors.

It is unclear how much the strike affected production, even as Indian laws prohibit the employment of contractors in core activities in most circumstances.

This is the latest unrest at an Apple supplier in India in recent years after food poisoning among workers triggered a strike at Foxconn and workers at a Wistron plant protested against alleged wage underpayment. (Reporting by Praveen Paramasivam in Chennai; Editing by Sohini Goswami)