EU calls for Ireland to remain in Single Market and Customs Union to avoid hard border.
The paper says that in order to avoid a hard border it is essential that there is no difference in rules for either side of the border.
It also explicitly spells out the fact that to avoid a hard border will take more than technical arrangements as favoured by the British Government: NI must be within the single market.
The question of protecting the Good Friday agreement is also addressed; Both the UK and the EU named this as a priority.
The Irish Foreign Affairs Minister, Simon Coveney, said that talk of individual countries vetoing a move to the next stage of negotiations is "unhelpful" but progress still had to be made on the border issue.
The Commission document will place more pressure on the Conservative government given its reliance on the DUP for survival.
Northern Ireland remaining inside the customs union and single market, while the rest of the UK was outside, would impose an entirely new structure on the United Kingdom.