Astronomers detect water vapour in atmosphere of Earth-sized exoplanet

Officials insist that the plan is fully funded, although the precise breakdown has not yet been published. A spokesperson said further details would follow "in due course".

International observers said the decision was being watched closely elsewhere, with several governments understood to be considering similar steps. "This sets a precedent," said a diplomat familiar with the discussions. "Others will now feel they have cover to act."

"There is no perfect option here, but doing nothing was never one of them"

The situation remains fluid. Further statements are expected later this week, and sources close to the process said that the timetable could still slip if key parties fail to reach agreement on the outstanding issues.

The roots of the current situation go back several years, to a series of decisions that were criticised at the time but attracted relatively little public attention. It was only when the effects began to be felt more widely that pressure for change started to build.

The background

A vote is expected before the end of the month. If it passes, the first changes would take effect early next year, with the full package in place by 2028.

The announcement came after weeks of speculation and follows months of negotiations between officials, industry representatives and campaign groups, several of whom had warned that any delay would carry significant costs.