When David Cameron made an election manifesto commitment to hold a referendum on Britain’s EU membership back in 2015, he faced accusations of putting his party before his country. In fact, European Council President Donald Tusk told the BBC earlier this year that even Cameron had acknowledged to him that it was about his own party.

The Conservative Party has long been split on the country’s relationship with the EU, with many opposing it from the outset and pressing for Britain to leave pretty much since it joined the union. In fact, hard Brexiteer Jacob Rees-Mogg’s father had even attempted to take the government to court to prevent Britain from ratifying the Maastricht treaty (the EU’s official treaty) in 1993.

Now, several years on both the Conservative Party and Labour remain as divided as ever, with the route ahead on Brexit revealing deep fractures that could have a profound long-term impact on them and on Britain’s political landscape.

Prime Minister Theresa May’s decision to engage in talks with the Labour leader Jeremy Corbyn this week has angered many MPs within her party, despite government insistence that they had been left with little choice but to do so after many Conservatives failed to back her withdrawal deal. Two ministers resigned in protest. Opposition centres around both the Labour push for customs union membership (which would allow for tariff free trade in goods that many businesses have long been seeking), as well as the calls for any deal to be subject to a confirmatory vote (i.e., another referendum). They also dislike the idea of a long delay to Brexit – which is also potentially on the cards – that would require the UK to participate in European Parliamentary elections on May 23.

Even ahead of the talks between the government and Labour, some Conservatives signalled that they might be willing to vote against the government if the Labour party brought a no-confidence motion in the government to Parliament (this is of course off the table now that talks are underway). David Davis, the former Brexit secretary, estimated that up to 20 of his fellow Conservative MPs could vote against the government in such a vote. This would be despite the fact that it could trigger a general election, and despite the fact that some polls out Labour head of the Conservatives. A Deltapoll survey for the Daily Mail found support for Labour at 41 per cent to the Conservative’s 36 pre cent.

At the other end of the spectrum, other Conservative MPs fear the government hasn’t been flexible enough. On Monday, after the attempt to find a solution by putting different proposals to a vote failed, Nick Boles – the MP behind one of the alternatives – said he was leaving the Conservative Party because they weren’t willing to compromise. Three other MPs had already left the party earlier this year to join the Independent Group of MPs, which also brought together 8 former Labour MPs. They’re collectively pushing for a second referendum and have applied to become a political party called “Change UK.”

Within the government there are some who believe a referendum may offer the route ahead. Chancellor Philip Hammond told an ITV news programme earlier this week that the was a “credible case” for a referendum on any Brexit deal. Others have strongly disagreed: “ a second referendum would have a very corrosive impact not only on our politics, but on trust,” warned junior Brexit minister Kwasi Kwarteng in Parliament this week.

However, Brexit has proved just as divisive for the Labour Party. The shadow cabinet’s insistence that it wants to respect the result of the referendum has divided MPs. Some – particularly those with constituencies in the north of England that voted strongly to leave the EU – believe this is the right strategy, and some have even defied the party’s line and on occasion backed the government on its withdrawal agreement.

Others are critical of the party’s failure to come out decisively to support a second referendum — one of the factors that triggered the creation of the Independent Group. However, some are equally critical of the potential of a second referendum being raised by Corbyn in his talks with May. This week, 25 Labour MPs signed a letter to Corbyn urging him to avoid a second referendum that “would be exploited by the far right” and could hurt the party’s chances in the future. They point to a recent poll that suggested higher levels of support for a no-deal Brexit than for remaining in the EU outside London. Opinion is polarising and hardening,” they warned.

More recently, the party’s leadership has faced criticism for its insistence on ending freedom of movement with the EU —which enables EU citizens to live and work freely in the UK and vice versa. Labour (like the government) says it wants a managed migration approach. Among those condemning this approach is the group Labour for Freedom of Movement — whose members include five MPs. “European freedom of movement is far from perfect, it's limited and doesn't protect everyone. However, the answer is not to scrap or further limit it. The answer is to defend the rights we already have while campaigning to strengthen and level them up for all,” the group said in a statement this week.