Amber Rudd's suggestion that Norway-plus could be an alternative if Theresa May's Brexit deal is rejected has added momentum to the campaign.
But what is Norway-plus, would MPs back it and would it truly deliver on the promises made in the Brexit referendum?
Norway Plus is a compromise that has broad appeal to the pragmatic middle. It delivers a softish Brexit with a deal that preserves membership of the Single Market and keeps the union of the UK intact. 6/
— Nick Boles MP (@NickBoles) December 7, 2018
– Why is it called Norway-plus?
The idea is based on Norway's relationship with the European Union as a member of the European Free Trade Association (Efta) and European Economic Area (EEA).
Being in the EEA after Brexit would keep the UK in the single market, meaning goods, services and people could continue to move within the bloc in the same way as before, therefore limiting the potential disruption to the economy.
On top of that, the "plus" bit of Norway-plus would involve a customs union with the EU, which, combined with the single market elements, would avoid a hard border with Ireland.
– Who backs it?
A cross-party group of MPs including Tory Nick Boles and Labour's Stephen Kinnock have pushed the idea as a way of delivering Brexit – the UK will leave the European Union – while maintaining the closest possible relationship with Brussels.
The instruction given by 52:48 referendum vote is clear: move house, but stay in same neighbourhood. To leave EU's political project, but to retain full access to a market of 500m consumers. #NorwayPlus meets those aims, introduces a safeguard on FoM & solves Irish border issue pic.twitter.com/EuKHwpsNkj
— Stephen Kinnock (@SKinnock) December 6, 2018
Mr Kinnock has claimed that at least 10 Cabinet ministers would back it if Mrs May's deal is thrown out by MPs on December 11.
– Who opposes it?
Leave supporters view Norway-plus as "Brexit in name only" because it keeps the UK tied to Brussels' rules, a customs union would restrict Britain's ability to strike trade deals around the world and there would be no end to the free movement of EU migrants to the UK.
EEA is a terrible idea for us:
"Far from being a compromise, the EEA option even without the Customs Union attachment (the plus of Norway plus) is even more restrictive for the UK than the PM's deal."
And what's the precedent for being in _both_ the EEA and CU? EU membership... https://t.co/JN8EzGX13V
— Steve Baker MP (@SteveBakerHW) December 8, 2018
Remainers who want a second referendum have also hit out at the option because they think a so-called People's Vote is the best way forward if the Prime Minister's plan fails.
– Could it happen?
Amber Rudd said it "seems plausible not just in terms of the country but in terms of where the MPs are".
"Norway Plus will leave us lobbyists camped outside of the European Parliament"
— People's Vote UK (@peoplesvote_uk) December 7, 2018
The current make-up of the House of Commons means that Mrs May's deal looks set to be rejected and MPs are also expected to block a no-deal exit, leaving Norway-plus and the second referendum as two of the possible options on the way forward.
Brexiteers will continue to push for a looser free-trade arrangement but that could still leave issues around avoiding a hard border with Ireland.
It is unclear which, if any, option could secure a majority in the House.