The British government will not revoke the UK’s withdrawal from the European Union once the formal process has begun, a spokesman for the Prime Minister has said.

The announcement comes in the wake of a call by former Prime Minister Tony Blair for Britons to “rise up” against Brexit, either by softening it or blocking it altogether.

Although the option to go against the decision remains officially open, some EU officials have said that they would not be open to a U-turn. A senior EU diplomat has said: “This bus has left.”

“No one is happy about it. But we have moved on and the last thing anyone wants now is to reopen the whole issue.”

In October, chair of the Council of EU national leaders Donald Tusk said that, while the 27 member states of the EU would welcome a British change of heart, a “soft Brexit” was not an option. He said that the choice for the UK was between a “hard Brexit or no Brexit”.

Prime Minister Theresa May has said that Article 50 of the EU treaty will be triggered at the end of March, starting departure negotiations that the government estimates will take two years.