BERLIN, Nov. 19 (Xinhua) -- Building cleaners in Germany have declared a nationwide warning strike over demands for Christmas bonuses, the industrial union for construction, agriculture and environment (IG BAU) announced on Monday.

IG BAU is demanding a Christmas bonus as an additional payment of around half a month's wage for the approximately 450,000 commercial building cleaners in Germany. Currently, the building cleaning sector is one of the few branches in Germany, where there is no collectively agreed Christmas allowance for employees.

"Most of the employees in the cleaning sector work in the lowest wage group. They work reliably and hard," said IG BAU federal board member and chief negotiator Ulrike Laux. Therefore, a Christmas bonus would be "particularly important for them as a recognition for their efforts," he added.

At the beginning of November, the German Federal Guild Association of the Cleaning Trade (BIV) rejected IG BAU's demand for Christmas bonuses. In a press release, BIV pointed to wage increases that had already been stipulated, which aim to balance out wage differences of building cleaners in eastern and western Germany by 2020. In addition to these wage increases, there would be no economic scope for Christmas bonuses.

"We expect the employers to understand in the meantime that this sector needs to be more attractive. It will certainly not do so with dumping methods," Laux added.