Technology giants Apple Inc are to be formally investigated over its tax arrangements in Ireland, the European Commission has said.
Last year it was revealed the company had cut billions from its tax by declaring companies in Cork and not tax resident in any other country.
The EU's competition authority has been looking into corporate tax arrangements in several member states.
More top news
The chancellor now faces the prospect of forming a minority government or calling for a snap election.
The 73-year-old said a return is unlikely "given the politicised atmosphere that seems to have afflicted our set."
Chancellor Philip Hammond said the UK will make a financial proposal to the EU in the next three-and-a-half weeks.