The politician said the Prime Minister “will not able to deliver” with regards to a favourable Brexit deal after insisting Labour was the only opposition that could challenge Mrs May on the terms in which the UK leaves the EU.
When asked about the Labour Party underperforming in polling figures, Ms Thornberry said it was not set in stone with the Prime Minister’s “so-called plan” set to “unravel”.
“Let’s see what happens in relation to this so-called plan,” she told Radio 4’s Word at One. “At the moment, Theresa May is getting good press and she’s been able to come out and say ‘I have a plan’ – but it unravels.
Emily Thornberry does not believe Theresa May is the person to deliver a successful Brexit
All it is, is a series of aspirations – there is no plan as to how she’s going to do it
“Because all it is, is a series of aspirations – there is no plan as to how she’s going to do it.
“It is fundamentally contradictory and she will not be able to deliver, we don’t think. We will do everything we can to ensure we get the best deal possible for Britain but it’s going to be hard.”
The Islington South and Finsbury MP also denied Ukip running in the Stoke-on-Trent Central by-election was a threat to her party, with the party’s leader Paul Nuttall reportedly set to stand.
The constituency voted heavily to leave the European Union last June, fuelling speculation that Ukip could seize a second parliamentary seat.
May's Brexit speech: Europe reacts
Tue, January 17, 2017
Politicians and celebrities tweet their reaction as Theresa May unveils her 12 point plan for Britain leaving the EU.
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The British Prime Minister Delivers Her Brexit Speech
Theresa May said the UK will be leaving the single market in her landmark Brexit speech
Ms Thornberry said: “No, I don’t think so, so as long as we get out there and we put forward our messages.
“We are the party that can hold this Government to account if we focus on the things that affect people in their day-to-day, which is particularly the health service and the threats to the local hospital.
“If we talk about the European Union in terms of jobs and we also make it clear that a plan is not just a piece of paper that says ‘plan’ on the top.”
The by-election comes after Labour MP Tristram Hunt quit the post and look up a role as director of London’s Victoria and Albert Museum earlier this month.