Jane Merrick is a British political journalist and former political editor of the Independent on Sunday newspaper. The opinions expressed in this commentary are hers.

(CNN) The debate over Brexit among UK politicians has become so toxic that the Prime Minister and leader of the opposition have more in common with each other than they have with their own parties.

With just weeks to go before a Brexit deal needs to be signed, Theresa May's plans for leaving the European Union have hit a brick wall. Some believe that she has as little as 48 hours to reach an agreement with Brussels, or risk having to spend millions in preparation for a no-deal.

In 137 days, the UK will leave the EU, whether or not an agreement between the two has been reached. And given the deep divisions between politicians of all stripes in London and the fast-approaching deadline, a no-deal Brexit has never looked so likely a prospect.

An emergency meeting of May's Cabinet, scheduled for Tuesday, to approve the latest version of the deal has been postponed.

Barely a day goes by without a Conservative MP proposing a different version of what Brexit should look like, and whether the final deal should be put to the British people in a second referendum.

Jeremy Corbyn, the leader of the opposition, gave an interview to a German magazine over the weekend, declaring that Brexit cannot be stopped. This goes against his own Labour Party's official line.

The problem with Brexit, as the Prime Minister is finding to her cost, is that it has been impossible to find a blueprint for EU withdrawal that makes all factions in all parties happy -- or, more seriously, is not furiously opposed by at least one of those factions.

In any vote she puts to Parliament, she needs 320 MPs from all parties to back her. There are 150 Conservative MPs who are ministers and government aides and are therefore obliged to either vote with her or resign. This means she is far short of a guaranteed Commons victory. Given the state of revolt in her party at the moment, she has a lot of work to do.

For Brexiteers such as Boris Johnson, who resigned as foreign secretary in July, May's compromise Brexit plan -- known as Chequers -- gives Brussels too much control over the UK even after Brexit.

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In his latest article on the subject, Johnson said Britain would be forced to "remain in captivity" by Europe because a safety mechanism, or backstop, would tie the country into a customs union with the EU indefinitely.

There are at least 50 Conservative MPs who feel the same way -- enough to cause trouble for the PM but, crucially, not enough to win an overall majority for a hard Brexit when the final deal is put to a vote in the House of Commons.

Johnson's younger brother, Jo, has put himself at the head of the other side of the debate, inside the same party. Jo Johnson resigned as transport minister on Friday, declaring the Prime Minister's "failure of statecraft" was the worst since the Suez crisis, one of the most calamitous moments for the British government in the last century. He said May's Brexit plans were a choice between "vassalage or chaos," and the risk of a damaging no-deal was so high that there should be a People's Vote -- a referendum on the final deal.

These Conservative MPs in the remain/soft Brexit camp are a smaller group than their Brexiteer colleagues, but, given May has no overall majority in the Commons, every MP's vote counts.

Even putting aside the rebellious factions in the Conservative Party, the issue of Northern Ireland is proving to be the sticking point in Brexit negotiations between the British government and Brussels. There is still no agreement on whether the Irish backstop -- the mechanism that would ensure Northern Ireland remains inside the EU customs union after Brexit to avoid a hard border with Ireland -- should apply to Northern Ireland only or the whole of the UK, and whether there is a further safety clause -- a backstop to the backstop -- to allow the UK to end this commitment.

The Northern Ireland Democratic Unionist Party, whose MPs have 10 votes in the Commons and are the only reason May has a theoretical majority in Parliament, are vociferously opposed to any backstop that leaves the province cut off from the rest of the UK.

And then there is Corbyn's Labour Party, the official opposition in the Commons, which has as much Brexit disunity in its own ranks as the Conservatives. The Labour Brexit policy, agreed at their party conference in September, is for all options to remain on the table, including a second referendum. Yet last week, Corbyn gave an interview to Der Spiegel declaring that Brexit could not be stopped.

On Monday, Sir Keir Starmer, the shadow Brexit secretary, insisted that Brexit could, in fact, be halted if the deal on the table did not meet Labour's demands. There are a handful of pro-Brexit Labour MPs who would vote with their Conservative counterparts, but the rest of Labour's 257 MPs are unpredictable, ranging from those who are loyal to Corbyn to those who are loyal to the EU and will block Brexit at any cost.

Some MPs want to revoke Article 50, the triggering mechanism which set the path to Britain leaving the EU on March 29, 2019, because Brexit is in such a mess.

Neither main party is officially advocating this as a policy, but the lack of agreement on all sides leaves a stalemate which, effectively, means an orderly Brexit cannot go ahead. In the Commons, there is no majority for a hard Brexit, soft Brexit, a People's Vote or remain.

It is a parliamentary impasse verging on a constitutional crisis. Brexit can never be solved because too many people disagree with all possible outcomes.

And so, in the absence of any deal, and without a revoking of Article 50, Britain crashes out of the EU on a no-deal basis -- a scenario that has alarmed national and international businesses and inside Britain's machinery of government and public services, due to the prospect of swingeing tariffs on goods at the border, miles of queued lorries and stockpiling of food and medicines by panicking householders.