LONDON — There was one dissenting voice when Theresa May announced she was kicking out Russian diplomats — and it didn't belong to Vladimir Putin.

In the House of Commons on Wednesday, the prime minister received almost unanimous support for her handling of the attempted assassination of Russian double agent Sergei Skripal and his daughter. While her sanctions were not as tough as they could have been, and were condemned as "hostile" by Moscow, they managed the rare feat of uniting MPs of all stripes behind her.

Except for Jeremy Corbyn, that is.

The prime minister told MPs the Kremlin was “culpable” for the March 4 attack, using a military-grade chemical weapon developed in Russia that's 10 times more deadly than sarin gas. In response, May announced that 23 Russian officials would be ordered to leave the U.K. within a week, high-level diplomatic ties would be suspended and new powers to seize Kremlin-linked assets would be introduced.

Labour MPs quickly put down a motion backing the government's contention that Russia was responsible, in defiance of their leader.

The announcement reflects the limitations May faces as she retaliates to what she described as “an unlawful use of force by the Russian State against the United Kingdom.” Many of the options available for what she said would be a “full and robust response” would also damage the U.K.

For her actions to really bite, the British prime minister will need support of international allies, whom she has publicly courted in recent days.

Looking tough at home, however, is a different matter and for a prime minister under pressure without a majority in parliament and consumed by Brexit negotiations with the European Union, a security crisis on the international stage is an opportunity she cannot afford to miss.

As a mood of national crisis gripped the Commons Wednesday, May succeeded in uniting MPs, who put aside their differences to support the prime minister. The Scottish National Party, Democratic Unionists, Liberal Democrats and Labour rallied to her cause.

Corbyn, in stark contrast, equivocated.

The Labour leader’s response defied the usual rules that normally govern such occasions. He questioned why the Russians had not been given a sample of the nerve agent as they had requested and wondered whether more diplomatic resources could have helped prevent the escalation of tensions between Moscow and London.

His spokesman later questioned whether Russia was really behind the attack at all.

'Appeasement'

MPs greeted Corbyn's comments with a torrent of abuse and cries of "shame" from the Conservative benches. There was barely disguised fury from his own side too.

While the House of Commons does not always accurately reflect the political divisions in British society, the overwhelming anger at the Labour leader may yet prove decisive for the prime minister, reopening old wounds in the Labour Party and uniting the Tories against the enemy at the gates.

One Conservative minister said Corbyn had strengthened May’s hand in parliament — which still holds the future of Britain’s relationship with Europe, and the government’s survival, in its hands.

Conservative MPs who are deeply uneasy with May's Brexit agenda may feel unable to vote against the government on key amendments or the final deal with Brussels for fear of easing Corbyn’s path to power, he said, adding: “The anger on my side was palpable. Corbyn is not fit to govern and many on his side agree with us.”

In the chamber itself Corbyn faced open hostility. The Tory MP Mark Francois said he was “an apologist for the Russian state.” The DUP’s Sammy Wilson accused him of adopting “a policy of appeasement.”

On the Labour benches, MP after MP stood up to side with the prime minister rather than their own leader. Ben Bradshaw, a former minister and long-time Corbyn critic, rose to tell May “most of us on these benches fully support the measures that are being taken.”

A spokesman for Corbyn later cast doubt on the government’s claims that the Russian state was responsible for the attack. “The break-up of the Soviet state led to all sorts of material ending up in random hands,” the spokesman said. “There is a history of WMDs [weapons of mass destruction] and intelligence which is problematic.”

The result: Corbyn has found himself split from his party again, as if his triumphant exceeding of expectations during the 2017 general election never happened.

Shortly after the debate, one Labour MP texted: “Jeremy Corbyn is a danger man and those around him are dangerous people. National security was always his Achilles heel. He does not speak for me.”

Another Labour MP — a shadow minister — said Corbyn’s response was “Student Union, pro-Soviet nonsense.”

Labour MPs quickly put down a motion backing the government's contention that Russia was responsible, in defiance of their leader.

Russian contempt

The prime minister isn't out of danger, however. Corbyn has taken on the Tories over national security before — and won.

During the general election he infuriated Labour MPs by criticizing U.K. foreign policy in response to the Manchester terror attack and turned the tables on the prime minister by attacking her record of cutting police numbers.

The second, longer-term concern for the PM will worry Downing Street and government security officials more. What if her “robust” response Wednesday proves inadequate to deter further attacks from Russia?

While lawmakers in London praised her response, in Moscow the move was greeted with contempt.

The Russian Embassy in London said it was a “hostile action” and “totally unacceptable, unjustified and short-sighted.”

Russian opposition leader Alexey Navalny wrote on social media: "23 Russian diplomats will be expelled from London. 23 Russian oligarchs and corrupt bureaucrats will remain to enjoy life in London.”

Veteran Conservative MPs Ken Clarke and Dominic Grieve warned that the prime minister’s actions alone would do little to dissuade the Kremlin from striking again and that only coordinated international action would work.

Clarke said Russia’s deployment of chemical weapons in the U.K. was a “serious threat to the safety of Western world.”

May’s biggest challenge ahead, security experts believe, is building an alliance to challenge Moscow. The prime minister told MPs she had begun this work by securing the support of Donald Trump, Angela Merkel and Emmanuel Macron.

NATO also released a statement expressing “deep concern at the first offensive use of a nerve agent on Alliance territory since NATO’s foundation.”

May’s challenge at home may have gotten easier, but her problems abroad may be only just beginning.