More than 5,000 nonregular workers at the Bank of Tokyo-Mitsubishi UFJ were allowed to join its labor union at the end of March so they can seek better working conditions, union sources said Friday.

It is the first unionization of nonregular workers at a major Japanese bank. Its labor union decided in March last year to accept nonregular employees and called on them to join. Of about 11,500 nonregular workers, over 5,000 agreed to join the union, the sources said.

Nonregular employees joining the company from now will also be able to unionize, the sources said. Such workers are involved in over-the-counter and other services at the bank's outlets and account for about one-fourth of its total workforce of around 48,000.

Management has approved the move, as it believes retaining skilled nonregular workers is important to customer service, the sources said.

In the latest spring wage talks, management decided to raise the pay scale by 0.5 percent, but the wage increase has been limited to regular employees.

Reflecting growth in corporate earnings, other major companies are also trying to retain nonregular workers by improving their labor conditions, with Fast Retailing Co. planning to turn about 16,000 of the 30,000 part-timers at its Uniqlo casual wear chain stores in Japan into regional regular employees.