Britain could be sued for up to millions of pounds if Brexit negotiators begin discussing trade deals with other countries before the country formally leaves the European Union.

There is a “high risk” of the EU taking Theresa May’s government to court if it begins negotiating trade deals with countries the 28-nation bloc is already negotiating with, according to documents leaked to the Times newspaper.

Liam Fox, the Tory minister who oversees the Secretary of State for International Trade, has been advised to delay negotiations with countries like the US as pressing ahead while Britain remains an EU member state risks a huge confrontation with Brussels, which could result in whopping multi-million-pound fines.

The documents reveal that Britain could face legal action for simply taking to other countries, even without striking trade deals. It is the latest, and perhaps most clear indication, of how confrontational Brexit talks could prove to be.

The document, the Times reports, warns that failure to comply would result in “infraction proceedings brought by the European Commission” and “infringement actions by member states”. It says: “The legal consequences would be that the UK would be required to pay a fine.”

To make matters potentially even worse for May, “infringement actions by member states” means individual EU member states could launch legal cases of their own against Britain.

The severity of the EU’s threats has already forced Fox to delay negotiating a trade deal with the US. Any plans the British government had of negotiating with Canada, Japan, and nations in southeast Asian are set to be pushed back too.

It has been a tough week for May as she struggles to take the Brexit process forward. The EU parliament appointed Guy Verhofstadt as its chief Brexit negotiator earlier this week — a “staunch federalist” who is adamant Britain will not be allowed to have single market access and opt-out of the free movement of people.

Yesterday, at a meeting of European leaders at an EU summit, Slovakian Prime Minister Robert Fico, along with the leaders of Hungary, Poland, and the Czech Republic, promised to veto any Brexit deal which would undermine the right of their citizens to travel freely to Britain.

Nobody in British government seems to know exactly what Brexit means at the moment. For May, it means a huge headache.