European Commission President Jean-Claude Juncker and Luxembourg Prime Minister Xavier Bettel sharply criticized British Prime Minister Boris Johnson Tuesday for failing to present any concrete proposals for extricating the United Kingdom from the European Union as Britain’s Supreme Court considered whether Parliament was suspended legally.

Johnson submitted a withdrawal agreement to Brussels but with details sorely lacking to keep EU leaders from rejecting it out of hand.

The Guardian reported the two sides have been talking about a “backstop” plan to prevent the implementation of a hard border between Northern Ireland and the Irish Republic if no deal on Britain’s exit from the EU can be reached on trade and security arrangements. The UK and EU have signed on to the idea, but Johnson’s team is not expected to submit a legal text until just two weeks before the Oct. 31 separation deadline.

Johnson canceled a planned press conference to avoid protesters and instead faced mocking from Bettel, who stood next to an empty podium as he engaged with reporters.Boos and jeers followed Johnson as he left a working lunch with Juncker, who had told Johnson it was his responsibility to present legally operational solutions.

Bettel rejected Johnson’s claims of progress in recent weeks. Johnson is against extending the Oct. 31 deadline and has rejected a do-over of the 2016 referendum that called for an end to British membership in the EU.

“People need to know what is going to happen to them in six weeks’ time,” Bettel chided. “They need certainty and they need stability. You cannot hold their future hostage for party political gain.”

Johnson has pushed for a no-deal Brexit despite government documents indicating such action would have a negative impact on food and fuel supplies and lead to social unrest. Before he suspended Parliament, lawmakers adopted a law to prevent crashing out of the EU without a deal, but Johnson has said he’s prepared to defy the law.

In a statement following their lunch, Juncker issued a statement saying it’s Britain’s responsibility “to come forward with legally operational solutions that are compatible with he withdrawal agreement.” He said the EC remains available for discussions round the clock. Johnson Tuesday agreed to further discussions with German Chancellor Angela Merkel next week on the sidelines of the U.N. General Assembly.

Opposition lawmakers in Britain have accused Johnson of suspending Parliament to silence debate. Parliament is not scheduled to be back in session until Oct. 14 and despite two lower court defeats, Johnson has said he has no intention of calling members back earlier.

The Supreme Court took up the issue Tuesday, with lawyers for Johnson maintaining he has every right to suspend Parliament after lawmakers refused to go along with his demand for new elections.