The EU will demand that European law continues to apply in the UK during the planned transition period after it leaves the bloc, according to the latest Brussels negotiating guidelines.
The guidance, obtained by Channel 4 News, says any changes to the EU "acquis" - the accumulated body of case law and legislation - should "automatically" apply to Britain during the transition, even though it will have no say in the decision-making process.
The confirmation that the UK will have to abide by any new EU laws and rulings by the European Court of Justice (ECJ) during the transition - expected to last almost two years - will heighten the concerns of pro-Brexit Tory MPs.
On Wednesday, Jacob Rees-Mogg, chairman of the influential pro-Brexit European Research Group, clashed publicly with Brexit Secretary David Davis, warning that Britain would be reduced to a "vassal state" of the EU.
Mr Davis, who is to make a major speech on Friday setting out the Government’s approach to the next phase of the negotiations, sought to play down the concerns, arguing that the EU legislative process was so slow there was unlikely to be any major changes during that period.
The document obtained by Channel 4 News, states: "The Union acquis should apply to and in the United Kingdom as if it were a member state.
"Any changes to the Union acquis should automatically apply to and in the United Kingdom during the transition period."
The guidance, setting out the negotiating mandate for the EU’s chief negotiator, Michel Barnier, for the transition talks, is expected to be formally adopted by foreign ministers of the remaining 27 member states in Brussels on Monday.
It states that the "full competences" of the EU institutions - "in particular" the ECJ - should be preserved during the transition period, which should not run beyond December 31 2020 - 21 months after Britain formally leaves the bloc.
It states: "The United Kingdom will however no longer participate in or nominate or elect members of the Union institutions, nor participate in the decision-making of the governance of the Union bodies, offices and agencies."