Boris Johnson has reportedly been given one week to improve his latest Brexit plan or EU leaders will not discuss it at a summit in two weeks' time.

European officials issued the ultimatum last night after Michel Barnier, the EU's chief Brexit negotiator, said the UK government needed to "fundamentally alter its position" if it wanted to secure a deal.

He told ambassadors that the UK's "meaningless" plan was "not operational in any way."

Johnson called his new plan a "compromise" but EU officials and the Irish government have indicated they cannot support it because it would involve introducing customs checks on the island of Ireland.

LONDON — European Union officials have given Boris Johnson one week to improve his proposed Brexit deal or European leaders will refuse even to discuss it at a crunch summit in two weeks.

The warning over the United Kingdom's new proposals, which were tabled this week, means there will almost certainly not be time to reach a deal by the October 31 deadline, the point by which Johnson made a "do-or-die" pledge to leave the EU when he became prime minister.

European ambassadors issued the October 11 ultimatum on Thursday evening after Michel Barnier, the EU's chief Brexit negotiator, said the UK government needed to "fundamentally alter its position" before negotiations could take place, the Times newspaper reported.

Barnier reportedly told ambassadors that the UK's "meaningless" plan was "not operational in any way."

On a tour of Paris, Berlin and other capitals next week, Johnson will appeal directly to EU leaders to support his new "compromise" plan, which he has described as a "fair" and "reasonable" offer.

Johnson wants the EU to scrap the backstop — an insurance policy designed to keep a free-flowing border on the island of Ireland — and replace it with his proposals for managing the Irish border after Brexit.

What are Johnson's proposals?

Under his plan, sent to European Commission President Jean-Claude Juncker Juncker on Wednesday, there would be two new borders after Brexit if new trading arrangements were not in place: a customs border between Northern Ireland and Ireland, and a regulatory border between Northern Ireland and Great Britain.

This is because the Northern Ireland would leave the customs union with the rest of the UK but continue to follow swathes of European single market rules covering agricultural and industrial goods.

This arrangement would kick in at the end of the transition period in December 2020, should parliamentarians in the Northern Irish Assembly vote for it. They would then vote on whether to continue with those arrangements every four yeas.

While the EU Commission has not rejected Johnson's proposals outright, many senior figures have indicated that they are unworkable and perhaps even dead on arrival, because it would involve customs checks on the island of Ireland, which would appear to contravene the terms of the Good Friday peace agreement.

Donald Tusk, European Council President, said the EU would stand "fully behind" the Irish government, which is against the proposals.

"My message to Boris Johnson: we remain open but still unconvinced," he said, following a phone call with Irish Prime Minister Leo Varadkar.

Varadkar questioned Johnson's pledge that there would not be "any new physical infrastructure on the island of Ireland linked to customs or customs checks."

He said that commitment "is actually in contradiction to the papers presented by the UK government."

Guy Verhofstadt, the European Parliament's chief Brexit co-ordinator, said the new proposals were a "repackaging of bad ideas that have already been floated" and "nearly impossible" to implement.

Read more: The European Parliament has 'grave concerns' about Boris Johnson's 'nearly impossible' Brexit deal

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And Norbert Röttgen, the chair of the German parliament's foreign affairs committee and a close ally of Chancellor Angela Merkel, said Johnson would not have time to secure a deal before October 31.

"One thing is clear: Johnson's Brexit plan can't be negotiated [before] October 31. If UK is serious about this, it must seek extension," he tweeted on Thursday.