London - British Prime Minister Boris Johnson on Tuesday condemned the "vile" racist chanting during England's Euro 2020 qualifier in Sofia as his Bulgarian counterpart urged the country's football chief to resign.
England eased to a 6-0 victory over their hosts on Monday but the game was overshadowed by offensive chanting from the stands, forcing the match to be halted twice in the first half.
"The racism we saw and heard last night was vile and has no place in football or anywhere else," said Johnson's spokesman, referring to monkey noises and apparent Nazi salutes that marred the match.
"The England players and management showed tremendous dignity and the prime minister commends the players who were targeted with this despicable abuse for their response."
The spokesman called for tough action from European football governing body UEFA, backing the Football Association's call for an urgent investigation with tough penalties.
Amid the fallout from the game, Bulgarian Prime Minister Boyko Borisov urged the country's football union president Borislav Mihaylov to quit.
"I urge Borislav Mihaylov to hand in his resignation immediately!" Borisov wrote on Facebook, adding it was "inadmissible that Bulgaria... is associated with racism and xenophobia".
Borisov said the government would sever all ties, including financial, with the Bulgarian Football Union (BFU) over what he called "a shameful loss" and the overall poor standing of Bulgarian football until Mihaylov resigned.
He tweeted his condemnation of the behaviour of some of the fans, saying it was "unacceptable" that Bulgaria, which he described as "one of the most tolerant countries in the world", should be associated with racism.
After several English players suffered racist abuse in a qualifier away to Montenegro in March, England manager Gareth Southgate had prepared his side to follow UEFA's three-step protocol for reporting racist incidents that can lead to matches being abandoned.
Southgate said after Monday's win that his side had made "two statements" by winning the game but also raising awareness of the situation.
"The game was stopped twice and I know for some people that won't be enough, but I think we were as a group on board with that process," he said.
Bulgaria coach Krasimir Balakov said he did not hear anything as he was focusing on the match.
"If this is indeed proven, we must apologise and be ashamed that such racist things happen in Bulgaria," he said.
"That's the truth.
"I am absolutely in favour of strict punishments if such things happened. But this has to be proven, otherwise it's speculation."
Anti-racism group Kick It Out said the match should have been abandoned by officials after TV footage showed that racist abuse continued in the second half.
"There can be no more pitiful fines or short stadium bans," the group said. "If UEFA care at all about tackling discrimination... then points deductions and tournament expulsion must follow.”
A section of 5 000 seats at the Vasil Levski National Stadium was already closed for the game after racist incidents during games against Kosovo and the Czech Republic in June.
With England 2-0 ahead, the game was temporarily stopped and a warning played over the loudspeakers in both Bulgarian and English.
That warning was not heeded and there was a second, longer stoppage of the match after Ross Barkley put England 3-0 up, with a number of Bulgarian 'ultra' fans ejected from the stadium.
Aston Villa defender Tyrone Mings was one of those targeted on his England debut.
"I am proud of how we dealt with it and took the appropriate steps," he said.
"I could hear it as clear as day. It doesn't affect me too much. I feel more sorry for those people who feel they have to have those opinions."
England now need just a point from their final two qualifiers against Montenegro and Kosovo next month to seal their place at next year's Euros.