Andrew Shepherd, senior power and renewables analyst at BMI Research, said the guarantee is a signal that Britain is still committed to nuclear energy, and this would help to give confidence to the French and Chinese investors.

"For a large project like Hinkley, to have a guarantee for some of the early-stage investment is helpful for investors, as it reduces the level of risk they have to bear," Shepherd said.

Premier Li Keqiang, meeting Osborne in Beijing after the dialogue, said the coordination of macroeconomic policies and financial cooperation between China and the UK, two major powers with global influence, will contribute to the stability of the global financial market.

Osborne is leading a large business and culture delegation on an extensive China trip that will also take him to Shanghai, Chengdu and Urumqi. Osborne said he hopes to make Britain China's "best partner in the West" and to share a "golden decade" together.

"It is a great example for international collaboration on the infrastructure of the future," Osborne said.

China and the UK also agreed to carry out a feasibility study on a stock-connect between London and Shanghai.

Zhao Yinan in Beijing contributed to this story.