May is due to map out a roadmap for the UK's relationship with Brussels after Brexit, sending a message of conciliation but reiterating her stance against the single market.
Duncan Smith told Julia Hartley-Brewer: Theresa May’s Brexit speech will embarrass the EU, which has behaved unbelievably badly.
All we've seen so far, he said, is "what the EU doesn't want" and in a negotiation "people that shout loud and rattle their tins [are showing] a weakness rather than strength."
In the EU, he added, "there is a panic about what’s going to happen when the UK leaves" and nothing they do or say can mask that reality.
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