15/01/2019 20:15 GMT | Updated 15/01/2019 22:55 GMT

How Theresa May United Rival Factions Of MPs Against Her Brexit Deal

From the DUP to Tory Remainers, here's how she lost support...

Theresa May has suffered an historic defeat over her Brexit deal at the hands of MPs from across the House of Commons.

So how did the prime minister manage to alienate so many different factions of MPs, from Tory Brexiteers to Labour Remainers?

Tory Brexiteers and the DUP – the backstop

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DUP leader Arlene Foster and Tory ex-Foreign Secretary Boris Johnson oppose the deal

The key objections to May’s deal surround the Irish backstop, which maintains a free-flowing border between Northern Ireland and the Republic if the issue is not solved by a free trade deal.

Both Tories and the DUP fear the UK becoming trapped indefinitely in the arrangement, as there is no end date and no mechanism for the government to trigger an exit in the deal

Tories fear this would torpedo Britain’s ability to strike free trade deals around the world as the backstop involves an all-UK customs union with the EU, which had actually been a demand of the prime minister.

The DUP meanwhile are enraged that May broke her promise not to draw a de facto border down the Irish sea, as the backstop will mean extra checks on goods travelling between the UK mainland and a Northern Ireland which will be following some EU single market rules.

Different shades of Tory Brexiteer also have numerous other objections to the deal, including paying a £39billion divorce bill to the EU without any clear direction on the type of future trade relationship, and the (albeit-limited) role for the European Court of Justice in the UK after Brexit.

Tory Remainers – searching for a reversal or a compromise

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Tory Remainers such as Anna Soubry are demanding a second referendum

Put simply, a handful of Remain-voting Tories including the likes of Dominic Grieve, Anna Soubry and Justine Greening believe Brexit will be a disaster for Britain and want people to be given the chance to reverse the decision in another referendum.

Others, such as Nicky Morgan and Nick Boles, back May’s deal but would also be happy with a softer Norway-style Brexit plan B, in which the UK remains part of the single market.

The joining together of these two groups to inflict defeats on the government over the process has made life difficult for May.

Labour frontbench and loyalists – no customs union

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Jeremy Corbyn made a permanent customs union his price for backing the deal

Jeremy Corbyn made clear his price for supporting the deal at Labour’s conference last autumn - a permanent customs union with the EU to ensure trade continues to flow freely and commitments to protect workers’ and environmental rights.

May’s deal does not deliver that customs union and so Labour will not support it.

But it it also clear the scale of opposition on May’s own benches presents Corbyn an opportunity to cause maximum havoc and potentially force a general election which could result in him becoming prime minister.

Labour Leavers – no prospect of the deal passing

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Labour MP Lisa Nandy represents Leave-voting Wigan but will not back the deal

Predictions that up to 40 Labour MPs in Leave-voting seats could end up backing the withdrawal agreement to avoid no deal but also deliver Brexit have not come to pass.

Although the likes of John Mann and Sir Kevin Barron back the deal, MPs like Caroline Flint and Lisa Nandy, who could bring more votes with them, have not moved to rebel.

It is thought that with the numbers stacked so high against the PM, Labour MPs felt there was little point rebelling and then losing. 

Labour Remainers – inferior to EU membership/Norway

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Labour Remainer Chuka Umunna was one of the earliest campaigners for a second vote

Like some of the Tory Remainers, Labour MPs like Chuka Umunna and Chris Leslie simply believe Brexit will harm the UK and so back a second referendum to give voters another chance.

Others like Stephen Kinnock and Lucy Powell believe a Norway-style Brexit would be a much better option than May’s “blind” deal which leaves the future uncertain. 

Other opposition parties – mainly anti-Brexit 

The SNP, Liberal Democrats, Green Party and Plaid Cymru all favour either no Brexit at all or a much softer withdrawal which keeps the EU inside the single market.

They were never likely to vote for May’s plan and she was never counting on their support.