Those behind illegal emissions will face costs "too high to bear", Premier Li Keqiang said on Sunday.

The premier was referring to strengthened efforts to tackle air pollution in 2015, at a press conference for domestic and foreign reporters at the close of the third session of the 12th National People's Congress, the country's top legislature.

This year's green focus will be on the full implementation of the revised Environmental Protection Law, which became effective on Jan 1. Under the law, all companies with illegal emissions will be brought to justice and held accountable by making their costs too high to bear, Li said.

"We need to make sure that the law works as a powerful and effective tool to fight pollution," the premier said.

No one will be allowed to meddle with the efforts in curbing air pollution and environmental law enforcement will be strengthened, he said.