China's Communist-controlled parliament meets on Saturday to approve a new five-year plan to tackle slowing growth in the world's second-largest economy, as President Xi Jinping centralises power and narrows the spaces for public debate.

Economic strains will loom over the annual meeting of the National People's Congress (NPC), the rubber-stamp parliament, after China's gross domestic product expanded 6.9 percent in 2015.

That was its worst performance in a quarter of a century and a far cry from the years of double-digit increases.

Premier Li Keqiang is widely expected to declare a growth target of 6.5 to 7.0 percent for this year in his opening speech.

Such a range would give officials significant latitude to declare the target has been met in the face of mounting uncertainty.

The NPC is also set to adopt the 13th Five-Year Plan, a legacy of the Communist command economy that still provides China with a set of goals and targets.

Authorities have repeatedly pledged reforms, with the economy weighed down by lumbering state-owned enterprises, but such changes would come at a cost.

A government official said this week that 1.8 million workers are expected to be laid off in the steel and coal industries and the ruling party is always keen to prevent social unrest.

"The main function of the NPC this year is to calm public nerves after the economic jitters of the last few months," Kerry Brown, director of the Lau China Institute at King's College London, told AFP.

Critics suspect Beijing is weakening its yuan currency to make its exports cheaper, although Chinese officials deny the accusations.

A shock devaluation in August saw the normally stable unit guided down nearly five percent in a week, and was followed by another drop in January.

A stock market slump since the middle of last year, accompanied by large-scale government intervention, has also raised concerns.

"The leadership have been good at communicating in other policy areas, but on economics the narrative at the moment is confusing," said Brown.

- 'Core' leader -

But as growth has stumbled, the government has become markedly less tolerant of dissenting opinions, including from within its own ranks.

Xi has accumulated more power more quickly than either of his two immediate predecessors, Hu Jintao and Jiang Zemin.

In recent months various local officials have repeatedly called for him to be designated the "core" of the ruling party leadership.

The term has previously only been applied to Communist China's founding father Mao Zedong and economic reformer Deng Xiaoping.

"Xi will certainly try to further consolidate his power during the NPC," said Joseph Cheng, a former professor of political science at the City University of Hong Kong. "But there's been some resistance to Xi amassing even more power."

China's already tight muzzle on the media has tightened, and last month Xi visited the official news agency Xinhua, state broadcaster CCTV and party mouthpiece the People's Daily.

According to Xinhua he ordered journalists to focus on "positive reporting", and "speak the Party's will and protect the Party's authority and unity".

- 'Very expensive' -

Several laws are being formulated that will increase government control over society, including a cyber security bill that cites maintaining "social stability" as a major objective.

US officials have described the plan as "deeply troubling".

China has detained more than 250 lawyers and activists in a crackdown since July, and the UN's human rights chief has warned that Beijing appears to be locking up critics even if they have committed no crime.

Some of China's most vulnerable citizens are already feeling the low tolerance for dissent under Xi.

Cao Yongfang, 63, has been petitioning the central government for a decade -- at times being sent to labour camp -- after officials improperly evicted her from her land, she said.

Petitioners in Beijing have long been targeted during the NPC, but their treatment has worsened in recent years, she said.

"Now many of us get sent back to the town where we came from," Cao said outside the government bureau that handles petitioner cases.

"But getting back to Beijing is very expensive for people with nothing."