Jeremy Corbyn is considering backing remaining in a customs union with the EU that would prevent us from signing comprehensive trade deals with non-EU countries in his big speech coming up on Monday. Some Labour sources say Corbyn will back staying in “the” customs union, though Emily Thornberry has said on LBC tonight that Labour will seek to replicate “a customs union that looks pretty much like the current customs union”. Guido is told that Unite’s influence has been key to the decision-making process – they back staying in the customs union. There is also the possibility that Corbyn could back a referendum on the Brexit deal on Monday. Remainers think that with Corbyn’s support they have the votes to keep the UK in a customs union that essentially prevents us from taking back control of trade. Brexiteers in the government are very concerned about the situation and Number 10 has pushed back votes on the customs union as a result. This is a worrying situation – Tory Remainer rebels are faced with the choice of backing down or siding with Corbyn and potentially bringing down the government…