The BBC director-general will warn that the retreat of its World Service because of funding cuts has helped Russia and China broadcast “unchallenged propaganda”.

In a speech at the Future Resilience Forum, a non-partisan meeting in London attended by international political figures, Tim Davie will discuss the global importance of the BBC World Service, which operates across more than 40 languages.

While addressing the war in Ukraine and unrest in the Middle East, Davie is expected to say: “Free and fair reporting has never been more essential – for global democracy and for audiences of most need around the world.”

He will add: “Perhaps most worrying from the BBC point of view is that we can now see clear evidence of the fact that, when the World Service retreats, state-funded media operators move in to take advantage.

“What we are facing is an all-out assault on truth worldwide – and with it security, stability and democracy. And no one should underestimate the impact the BBC has had in the global news landscape to this point – as an entirely independent force …”

During his Monday afternoon speech, Davie will also discuss the impact and growth of news outlets controlled by Russia and China, and how they are outspending BBC investment “by a multiple of thousands”.

“Together they are spending an estimated £6-8bn on expanding their global media activities – investing hard to grow their audiences in key markets in Africa, the Middle East and Latin America,” he will say.

“Across Africa in particular, Russian media is incredibly active in promoting its narratives, with social media influencers amplifying propaganda and so-called ‘activists’ live-streaming pro-Russia rallies.

“And this investment is seeing significant returns, not only in terms of the reach of Russian state broadcaster RT and China’s CGTN, but also in terms of trust.”

In his speech, Davie will discuss how other companies have filled the “gaps” the BBC left in Africa after its “retreat”.

“Kenya’s state broadcaster KBC has taken up Chinese output on TV and radio, as has Liberia’s state broadcaster LBS,” he will say. “Meanwhile, in Lebanon, Russian-backed media is now transmitting on the radio frequency previously occupied by BBC Arabic.

“Last month, our outstanding BBC Monitoring teams listened in to that Russian output on the day thousands of pagers and radio devices exploded. What they heard was unchallenged propaganda and narratives being delivered to local communities.

“Had the BBC been able to retain our impartial radio output, these messages would have been much harder for local audiences to find. In this context, the further retreat of the BBC World Service should be a cause for serious global concern.”

In 2022, the BBC announced the proposed closure of about 382 posts at the World Service as well as the closure of its Arabic and Persian radio services.

In April an inquiry was launched into the future funding of the service, focusing on the corporation’s influence as a soft power and establishing whether increased government support was needed.

The World Service is the BBC’s international broadcaster and is predominantly funded by the UK licence fee. It receives additional grant funding of £104.4m from the Foreign, Commonwealth and Development Office.

Under its current support package, the World Service has agreed not to close any language services, but this condition is set to be lifted in 2025.