Speaking in Brussels, a delegation of bishops also voiced the importance of "face-to-face" dialogue during negotiations concerning the country's withdrawal from the EU.
Auxiliary Bishop for the Diocese of Westminster, Bishop Nicholas Hudson led the group in Belgium, which also included Bishop Tom Burns, Bishop Paul McAleenan and Bishop William Kenney.
Bishop Nicholas Hudson, who is the lead bishop on European issues, said: "The UK is still part of the EU and during the transitional period before the UK leaves there are vital issues to resolve.
"We will also continue to have a relationship with the EU and its institutions in the future so these face-face meetings are invaluable.
Meeting with officials from various EU institutions at a "key time" in Brexit talks, the group raised concerns around future trade deals, prisoner transfer rights and the Northern Ireland-Ireland border.
They also discussed the rights of EU nationals living in the UK and UK citizens living in European countries post Brexit.
The delegation also heard about the advocacy work undertaken by the Commission of the Bishops' Conferences of the European Community (Comece) on behalf of the Bishops' Conferences of the EU.