Tory ministers today blamed the threat of a new Salisbury-style attack for slowing down the system after issuing just 500 visas to Ukrainians since Friday.
Immigration Minister Kevin Foster said people in Calais are "pretending to be Ukrainian" with false documents in a bid to smuggle themselves into the UK.
And he raised the threat of a repeat of the 2018 poisoning with the nerve agent Novichok.
