Gordon Brown has said a “show of strength” is needed to face down Russian President Vladimir Putin over a possible fresh incursion in Ukraine.
The former prime minister recalled that Mr Putin’s attitude during his dealings with him was to say he “would not co-operate in any way”.
He believes that hard-hitting financial and economic sanctions which affect the Russian leadership may be needed to get Mr Putin to back off.
Mr Brown’s comments came after Prime Minister Boris Johnson and US President Joe Biden met virtually with the leaders of Nato, the EU, Italy, Poland, France and Germany on Monday in a bid to avert what is feared would be a bloody and protracted conflict for Moscow.
Mr Brown told ITV’s Good Morning Britain: “You have to be able to stand up to him (Putin). Remember the assassinations on British soil? He was going to assassinate other people if we hadn’t stood up to him. The only thing that Putin understands is strength.
“Perhaps, belatedly, the right thing to do is a show of strength from Nato and unity from Nato, and that is something that has got to be fought for and making it clear that we will not accept Russian incursions.
“I think it will be financial and economic sanctions that are going to have to be so severe that the Russian autocrats, the Russian oligarchs and Putin himself and his government is affected by them.”
Russian troops have massed at the border with Ukraine and intense diplomatic activity has failed to ease tensions.
Lord Dannatt, the former head of the British Army, believes the Russians “will not get an easy ride” if they invade.
He told Times Radio: “The Ukrainians are a proud people and their military has come on in leaps and bounds in the last few years, supported, to a fair degree, by Western equipment and training.
“There will be huge costs to the Russians if they decide to go into Ukraine, even just part of Ukraine. I think this is a factor they have to bear in mind.”
He thinks Mr Putin is currently failing in his aim to upset the Nato alliance with his stance on Ukraine by trying to get its partners “to start squabbling among themselves”.
Mr Putin may back off from an incursion of Ukraine because it could damage his popularity, he added.
Lord Dannatt believes “the Ukrainians will fight and fight hard” and that would mean Russian fatalities and casualties.
He added: “He (Mr Putin) is very powerful but he does not have universal popularity. There is quite an opposition movement to him.
“If Russian television screens get filled with body bags and casualties coming back from a bloody incursion in Ukraine, that will damage his popularity and damage his standing as opposed to boosting his position – so he has got a calculation to make.”
Downing Street has stressed that diplomatic discussion with Russia remains the first priority, but said the nation would be hit with “swift retributive responses” if a “further Russian incursion into Ukraine” takes place.
Under efforts to deter Russian “aggression”, Mr Biden said the leaders had discussed preparations to “impose severe economic costs” against Moscow while seeking to “reinforce security on the eastern flank”.
The Pentagon has put 8,500 US troops on heightened alert, preparing them for a possible deployment to reassure Nato allies amid rising tensions.
Mr Johnson has also said that “gloomy” intelligence suggests Russia is planning a lightning raid on Kyiv, as British staff and their families began leaving the Ukrainian capital.
He warned Mr Putin, who in 2014 led a Russian annexation of Crimea from Ukraine, that a fresh invasion would be a “disastrous step”.
“The intelligence is very clear that there are 60 Russian battle groups on the borders of Ukraine, the plan for a lightning war that could take out Kyiv is one that everybody can see,” Mr Johnson said.
“We need to make it very clear to the Kremlin, to Russia, that that would be a disastrous step.”