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) British Prime Minister Theresa May has lost two Cabinet ministers in the last two weeks , and the future of a third rests with an ongoing investigation into his conduct. A fourth is at the center of a growing diplomatic row with Iran.

This sense of crisis would hamper a government at the best of times -- even one that had a parliamentary majority, something May lacks.

But against this backdrop of disarray, the British Prime Minister has just been confronted with the prospect that she won't be able to get Brexit through Parliament -- meaning the entire project could fall into chaos.

Talks between officials from Britain and negotiators for the European Union have progressed slowly, and are now at a near-stalemate. The EU has given Britain a deadline of two weeks to agree on a figure for the so-called "divorce bill" -- the money May's government must pay into the EU budget as part of its membership obligations.

As negotiations with the EU reach the crunch point, May's government is finding itself in ever-deeper trouble over its attempts to push through the legislation that will allow leaving the EU to happen at all.

Lawmakers from all parties have put forward hundreds of amendments to the EU Withdrawal Bill, and debates and votes are expected to take a month. At the heart of the problem is that the lack of progress in talks between the UK and EU -- which must conclude by summer next year -- has meant that May's government has recently had to concede a new alarming reality: that the differences are so great that no deal may be done at all.

This prospect has made the many UK legislators who always feared that Brexit would be damaging to the UK even more fearful. Now they are worried that the UK will be stepping into a complete unknown with no transition deal or trade deal planned with the EU. But hardline pro-Brexiters still want the UK to leave, whatever the short-term damage. This is why the content of the Withdrawal Bill is now being even more strongly contested than it was just a few weeks ago.

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On Monday night, May's minister in charge of Britain's exit from the European Union, David Davis, attempted to buy off MPs worried about a "cliff edge" hard-Brexit -- under which the UK would leave all the EU institutions such as the single market, customs union and laws -- by promising they would by able to vote on the final deal agreed with Brussels on Brexit, including the cost to Britain of leaving and its post-Brexit trading rights.

Yet the move backfired, because it presented lawmakers with only two choices: backing whatever deal had been reached even if it was a bad one in their eyes, or voting against it, which would mean crashing out with no deal at all.

What a majority of MPs -- including the Opposition Labour Party -- want is to be able to ask to return to the negotiating table, or ask for a pause, or in some cases just agree to stay in the EU, rather than be forced to choose between what they see as two undesirable outcomes.

Many MPs -- including some Conservatives -- are also furious that the government is trying to enshrine into law the actual precise leaving date and time: 11 p.m. GMT on March 29, 2019.

This was put forward by May to appease hardline Brexiters who want reassurance that Brexit will definitely happen, but the moderates worry that it ties the UK's hands and commits it to exit and the prospect of high tariffs trade under World Trade Organization rules if no deal is reached.

The parliamentary difficulties for May are not unconnected to the problems inside her Cabinet. Both sides are hardening their positions because they know she is a weak Prime Minister.

Having lost her government majority in parliament, the sense of crisis caused by the resignation of Michael Fallon as defence secretary and Priti Patel as international development secretary has made it look like May is not in control of events. Her de facto deputy prime minister, Damian Green, is being investigated over allegations of sexual harassment and pornography.

The foreign secretary, Boris Johnson, is under pressure for incorrectly stating that a British-Iranian citizen, Nazanin Zaghari-Ratcliffe -- who has been jailed by Tehran -- was in the country training journalists when she was on holiday with her family.

For his part, the foreign secretary has tried to bolster his chances of survival by rekindling an alliance with another Cabinet minister -- a move which could be interpreted as the first strike against May's premiership.

Johnson and Environment Secretary Michael Gove, who together led the successful campaign for Britain to leave the EU last year, fell out over their own leadership ambitions.

But a memo leaked to a newspaper over the weekend revealed they are now working together to put pressure on the Prime Minister to deliver Brexit, fearing that Britain is heading toward a no-deal scenario without preparations being made for businesses, or even that Brexit may not happen at all.

The PM is reluctant to sack Johnson in case it leads to a revolt among his pro-Brexit supporters in her own party, and in turn triggers her own downfall. May is ultimately left with a rebellion both in Parliament and inside her own Cabinet -- and she is so weak she is running out of options.

Brexit has been a hugely contentious issue ever since the referendum divided the country in half. As it reaches its climax in Parliament and in Brussels, those divisions are sharper than ever.