Dominic Raab has dismissed fears that Vladimir Putin will use nuclear weapons in the Ukraine crisis, calling his threats “rhetoric and brinkmanship”.

       The Russian president alarmed the world by putting his arsenal on high alert – and, overnight, the Kremlin is reported to have claimed that Ukraine is developing a dirty nuclear bomb.

       But, asked if that suggested Moscow was seeking an excuse to use battlefield nuclear weapons, Mr Raab replied: “I think it is rhetoric and brinkmanship.”

       The Russian president had “a track record of misinformation and propaganda”, the deputy prime minister said.

       The comments came as Mr Raab also rejected calls for the UK to make a more generous offer to some of the million-plus refugees fleeing the conflict, saying it was “the wrong thing to do”.

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       The UK has refused to waive visa rules – in stark contrast with the EU, which has offered asylum to all Ukrainians crossing its borders for the next three years.

       Mr Raab claimed that extending the UK’s offer of help, beyond family reunions and a sponsorship scheme that has yet to start, would mean removing “security checks on those coming from a war zone”.

       “We have got to look at our security,” he told the Sky News programme Trevor Phillips on Sunday – claiming that the public would oppose the government putting in place more generous measures.

       “Public support has been incredible, very moving, overwhelming. I think you would start to see that fray,” Mr Raab said.

       Fiona Hill, a former member of the US National Security Council, is among Russia experts who have warned that Mr Putin would be willing to use nuclear weapons. “Every time you think, ‘No, he wouldn’t, would he?’ – Well, yes, he would,” she said recently.

       But Mr Raab brushed aside fears that an “isolated Kremlin” would reach for its most deadly weapons, saying: “No, I think the debate and rhetoric is just that.”

       The justice secretary again ruled out imposing a no-fly zone – despite the pleas of Ukraine’s president – which he said would lead to a “massive escalation” and would fuel Russia’s claims that it is fighting a war against the west.

       “We’re not going to get ourselves into a direct military conflict with Putin because that would be a massive escalation, but also that feeds Putin’s narrative,” Mr Raab argued.

       “Putin wants to say that he’s actually in a struggle with the west – he’s not.” No-fly zones are “very difficult, very challenging”, he added.

       Mr Raab also dismissed Mr Putin’s claim that the sanctions levelled against Russia were a declaration of war, calling them “both legally justified but also proportionate”.

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       He warned Russian commanders and Mr Putin’s close associates that they risk being prosecuted for war crimes at the International Criminal Court (ICC).

       “What they do now, whether they give or whether they follow illegal orders to commit war crimes, they will be held to account for it – and they need to know that,” Mr Raab said.