British Prime Minister Theresa May leaves 10 Downing Street in central London on Dec. 6, 2017, for Prime Ministers Questions in the Houses of Parliament. (Rain/Epa-Efe/Rex/Shutterstock/Rain/Epa-Efe/Rex/Shutterstock)

It is obvious that Prime Minister Theresa May is no longer negotiating with just the Europeans over Britain's messy exit from the union. Talks are far tougher at home — where she faces blistering arguments on all sides, including revolt among her own ministers.

During a question-and-answer session in Parliament on Wednesday, the leader of the opposition, the Labour Party's Jeremy Corbyn, declared that Brexit talks had become "a shambles."

More worrying for May, members of her own Conservative Party challenged her, too, wondering aloud whether she had the resolve to negotiate a tough, decisive exit from the European Union or was getting wobbly under the mounting pressure of deadlines coming next week.

One of the most insistent Brexiteers, the Tory parliamentarian Jacob Rees-Mogg, asked in withering diction whether the prime minister needed to "apply a new coat of paint to her red lines, because I fear on Monday they were beginning to look a bit pink."

His challenge to his leader was answered by jeers and harrumphing from the benches on both sides in the House of Commons.

Rees-Mogg was referring to the spectacular meltdown on Monday in Brussels, when May was just hours away from presenting a preliminary, Phase 1 kind of deal on exiting the European Union, only to have it snatched away by her coalition partner in government, the tiny Democratic Unionist Party of Northern Ireland. 

The unionists, who appear to have been kept mostly in the dark, rebelled at the last minute against vague but still meaningful language from May that was designed to maintain an open border between Northern Ireland, which is part of the United Kingdom, and the Republic of Ireland, which is in the E.U.

As May was fending off mockery in Parliament, the British political press reported that hard-line Brexiteers in her cabinet, led by Foreign Secretary Boris Johnson, were expressing "genuine fear," according to the Telegraph newspaper, that May was leading Britain toward a dreaded "soft Brexit."

Citizens of the U.K. approved leaving the European Union in a historic referendum in June 2016, by 52 percent to 48 percent. But the British public today — and political leaders most of all — continue to be divided and very unclear about the terms of the split.

There are many who want a "soft Brexit" — in which many of the existing arrangements between the U.K. and the continent are preserved, including the single market and the customs union — and others who demand a "hard Brexit," a decisive snip of the umbilical cord that has joined the two since 1972. They want a Britain "sovereign and free," they say.

There is also a large third group that considers the whole idea of leaving the European bloc a catastrophic blunder.

In Parliament, opposition leader Corbyn began his grilling of the prime minister on Wednesday by quoting her trade secretary, Liam Fox, who last summer said Brexit negotiations would be "the easiest in human history." 

Corbyn asked, his voice dripping with derision: "Does the prime minister still agree with that assessment?"

May replied, "Negotiations are in progress, and very good progress has been made." She said that only "a couple of things" need to be agreed upon with the Europeans before talks on trade and future relations can begin.

It was not only May in a harsh light, but also her Brexit secretary, David Davis, who on Wednesday was accused of misleading Parliament after he conceded that his government had not done a deep analysis, economic sector by economic sector, on the possible effects of Brexit — even after his repeated suggestions that such studies were ongoing.

On the question of what to do about the Ireland-Northern Ireland border in a post-Brexit world, confusion continued.

Arlene Foster, the leader of the Democratic Unionist Party [DUP], had a short telephone conversation with May on Wednesday morning. According to the Guardian, Foster had refused to take May's calls for 24 hours while the sides haggled.

Foster — who has said that her party will not accept any form of "regulatory divergence" that separates Northern Ireland from the rest of the U.K. — is expected to travel to London at some point for face-to-face discussions on the issue of the Irish border.

"There is still work to be done," said a DUP spokesman. 

The DUP is a far-right, pro-union party in Northern Ireland that has only 10 members in Parliament. But following a botched general election this year, May's Conservative Party now relies on the DUP to pass key legislation in Parliament.

In Dublin, Irish Prime Minister Leo Varadkar told lawmakers on Wednesday that the DUP does not represent everyone in Northern Ireland. The DUP backed Brexit in the E.U. referendum, but the majority of voters in Northern Ireland voted to "remain" in the E.U.

Varadkar told lawmakers that "we stand by the text agreed" and raised the possibility of trade talks being postponed until the new year.

 "We want to move to phase two, but if it is not possible to move to phase two next week, then we can pick it up in the new year," he said.

Karla Adam contributed to this report.