The condemnation came after an afternoon of Brexit meetings in Brussels.
The PM will return for more negotiations before end of February.
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Juncker and Barnier reject changes to existing agreement.
But PM warns Commons not to vote down her deal on Tuesday.
Theresa May attempting to win reassurances over backstop plan.
It comes a day after the UK cabinet discussed plans for a no-deal Brexit.
PM admits to 'robust' talks with EU chief.
PM still needs to get her deal through parliament.