MEPs have concluded it is the best solution to the problem of ensuring there is no border in Ireland. The move has the support of all major political groups.
It would mean continued free movement on the island of Ireland, with customs checks instead taking place at ports on the Irish Sea for visitors travelling between Great Britain and Northern Ireland.
The resolution rubbishes Britain’s existing proposals on the issue and is set to enrage DUP MPs propping up Ms May’s Government.
Both the UK and EU believe there should be no hardening of the border with the Republic, which is currently not policed – but disagree on how to do this while Ireland remains inside the EU’s borders and the UK leaves them.
European Parliament chiefs believe shifting border posts to Irish sea ports is the optimal solution.
Ireland is one of three issues where sufficient progress must be made before the EU will start trade talks.
The UK has published new papers that are vague on detail and not really different to ones published months ago.
The Irish Government is losing patience with the UK Brexit negotiations so is looking at solutions worked out with the EU.
Irish opposition politicians have called for the publication of an internal report by the country's customs authorities discussing the potential impact of Brexit.
The document reportedly says that an open border between Northern Ireland and the Irish Republic will be impossible from a customs viewpoint.
Irish Prime Minister Leo Varadkar tweets that the country is working to prevent a customs border " A customs border would be expensive, a barrier to trade and an obstacle to peace. That is why we are working to prevent it, with support of EU."