ABUJA (Reuters) - Nigeria's main labour union has rejected a government-approved 50% hike in telecommunications tariffs and announced plans for a nationwide protest on Feb. 4.

The telecoms regulator last week approved the increase in mobile tariffs, the first such hike in more than a decade, bowing to pressure from operators struggling with surging costs amid high inflation and currency devaluation.

In a meeting of the Nigeria Labour Congress (NLC) late on Wednesday, union leaders called the increase "insensitive, unjustifiable, and a direct assault" on citizens already grappling with the worst cost-of-living crisis in a generation caused by reforms instituted by President Bola Tinubu.

"The rally will serve as a warning on the dangers of imposing such an unfair increase on a struggling population, NLC President Joe Ajaero said in a statement, citing high food costs and hikes in the prices of petrol and electricity.

The union demanded the immediate suspension of the tariff adjustment and called for dialogue between the government, the regulator and union leaders.

Ajaero threatened a nationwide boycott of telecommunications services and a possible strike if authorities refused to engage in dialogue.

The NLC, representing millions of workers, has repeatedly clashed with the government over economic reforms which it says exacerbate poverty, but officials argue the measures are necessary to stabilise the economy.