According to Deputy Prime Minister Dominic Raab, there is a «very high» risk of Russia invading Ukraine.
This comes at a time when Britain has accused President Vladimir Putin of plotting to install a pro-Moscow leader as head of government in the neighboring country to Russia.
The British Foreign Office has taken the unusual step of naming former Ukrainian MP Yevvin Murrayev as a potential candidate for the Kremlin to take over the Kiev post.
Western allies have stepped up warnings that Russia will pay a heavy price if the estimated 100,000 troops on the border launch any kind of incursion into Ukraine.
Asked if he thought Russia would invade Ukraine, Raab told the BBC’s Sunday Morning programme: «I think there’s a very, very high risk of that.
The world should watch this and be very clear with President Putin that it will not do it without a cost, and that there will be a price.
«A price in terms of the hard defense that we expect the Ukrainians to bear, as well as the economic cost through sanctions, which of course would be more effective if the international community spoke as one or at least with broad consensus.»
In a statement on Saturday, Secretary of State Liz Truss said the Russian plot shows the extent to which the Kremlin was willing to go to undermine the government in Kiev.
«The information being released today highlights the scale of Russian activity designed to sabotage Ukraine, and is an insight into the Kremlin’s thinking,» she said.
Russia must de-escalate, end its campaigns of aggression and disinformation, and follow the path of diplomacy.
“As the UK and our partners have repeatedly said, any Russian military incursion into Ukraine would be a serious strategic mistake with huge costs.”
Vadim Prystaiko, Ukraine’s ambassador to the UK, said a Russian invasion was «very likely» but also told Radio Times that «there is still room for a diplomatic solution».
Prystaiko said Ukraine was «ready to fight» but said the country was not well-equipped for a long-term fight.
Trevor Phillips told Sky on Sunday that Ukraine would «absolutely» want to join the European Union and NATO, adding: «That’s what we made clear eight years ago, that’s why the Russians came, and that didn’t change our resolve even an inch.»
When asked what he thought the scale of the conflict could be, he said he still hoped these were just threats for now, but added that the country was preparing itself.
Murrayev, the media owner, lost his seat in the Verkhovna Rada when his party failed to get 5% of the vote in the 2019 elections.
He has reportedly spoken in the past of supporting Russia’s annexation of Crimea from Ukraine in 2014.
In addition, the British Foreign Office has named four other Ukrainian politicians who they say maintain links with Russian intelligence services.
She added that some of them were in contact with Russian intelligence officers working on the invasion plan.
Among them is Mykola Azarov, who served as prime minister under pro-Moscow President Viktor Yanukovych, who was ousted by a popular uprising in 2014.
Azarov fled to Russia, where he established what was widely seen as a puppet government in exile.
He was subjected to international sanctions and a «red notice» issued by Interpol at the request of the Ukrainian government.
Also on the list is Vladimir Sevkovich, the former deputy head of Ukraine’s National Security and Defense Council, who this week was the subject of US sanctions for allegedly working with Russian intelligence.
The others are Serhiy Arbuzov and Andrei Kluyev, both of whom served as deputy prime ministers under Yanukovych.
The Russian Foreign Ministry accused the British Foreign Office of spreading «disinformation».
She urged the State Department to «stop these provocative activities» and «stop spreading nonsense.»