Paul McKeever, Chairman of the Police Federation, has urged the government to take "urgent stock" of the results of a new study into the London riots.
He said that police would struggle to cope with further disorder if proposed austerity measures went ahead.
"This comprehensive analysis demonstrates what we have been telling the Government for two years now; that a 20% budget cut to policing will have a negative impact on public safety and that police numbers really do matter.
"Officers interviewed rightly identify and voice concern that, should the same circumstances occur again, the police service would struggle to cope and contain the situation with the loss of police officers numbers we are experiencing as a direct result of the cuts - over 5,000 last year alone."
More top news
The officer tried to hold off the group at Finsbury Park - where Drake and Mary J Blige were headlining.
The image, taken at the weekend, shows the man making his way past Big Ben with a girl perched on his shoulders waving an ISIS flag.
It was the moment the International Olympic Committee president broke French hearts and gave the 2012 summer games to London.