Parliament has failed to enact the outcome of the referendum vote of June 2016 in spite of having had over 3 years. They are now trying to enforce no deal whilst having no agreed upon alternative.
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This is undemocratic especially if they go back to the people but are taking an option off the table.
17.4 million people voted to leave the EU. Parliament has voted to enact this vote on two separate occasions and yet have still failed to deliver. Parliament cannot claim to have won a vote for democracy following the Supreme Court judgement and then not deliver on the referendum.