Britain's EU exit, due to take place last month, has been delayed as the government tries to win Parliament's backing for a divorce deal with the bloc.
Talks on a compromise agreement are resuming Tuesday between May's government and the main opposition Labour Party. But there are few signs the gap between the two sides is closing.
Anger is growing among Conservative lawmakers and officials over the delay to Brexit and May's bid for compromise.
Pro-Brexit Conservative lawmaker Nigel Evans says calls for May's departure are "growing into a clamor" and she should resign "as soon as possible."
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