FILE PHOTO - Irish Prime Minister Leo Varadkar (Taoiseach) speaks at a news conference with German Chancellor Angela Merkel during Merkel's visit to Dublin, where the latest Brexit developments were on the agenda, in Farmleigh House, Dublin, Ireland April 4, 2019. REUTERS/Clodagh Kilcoyne

BRUSSELS (Reuters) - Irish Prime Minister Leo Varadkar said on Thursday the United Kingdom would crash out of the EU on June 1 if it failed to hold European Parliament elections during a Brexit extension granted until the end of October, 2019.