The UK's football teams should boycott the 2018 World Cup in Russia because of the country's alleged involvement in the bombing of civilians in Syria's brutal civil war, Nick Clegg has said.
The former deputy prime minister called on Fifa to cancel the tournament because Russian president Vladimir Putin is "mocking the world".
If football's global governing body does not cancel the tournament, England, Wales, Scotland and Northern Ireland should boycott it, he said.
It comes after Foreign Secretary Boris Johnson accused Russia of being complicit in war crimes while supporting bombing by the Syrian regime led by Bashar Assad.
Mr Clegg told ITV's The Agenda: "We can weep at the pictures and have endless debates with the UN but the fundamental problem is that there is no cost to Russia.
"It might be a silly thing, it is ludicrous that Russia is going to hold the World Cup in 2018, what world are we in? That they basically abuse people's human rights on that scale, barbarism in Aleppo, and we will prepare to play football in Moscow in 2018?
"I think if Fifa had any moral mettle to it at all it will now say that Russia has forfeited any right to host any international tournament. I'm calling for Fifa to cancel Russia - if they don't, if Russia is behaving like this, of course we shouldn't turn up.
"It is a measure of how much Putin can basically mock the rest of the world, bomb Aleppo and still prepare for the World Cup in 2018."
His comments follow calls to boycott the 2022 Qatar World Cup over the Middle Eastern nation's treatment of migrant workers, and numerous corruption scandals involving the likes of Fifa and the English game.
Mr Clegg, the Liberal Democrats' Brexit spokesman, said leaving the EU would hinder efforts to curb Russian aggression.
"The best way to take on Putin is economics. What do they depend on? The EU market. We had much greater clout when we were enforcing sanctions collectively as Europe against Russia," he said.
"The great tragedy of many tragedies of us absenting from Europe is we will now not be as tough with Putin as we were when we were around the table."