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."
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A lamp in the tower which houses Big Ben is to be switched off for the first time in more than 70 years.
Sir Bruce entertained audiences for more than seven decades.
Work in the tower will also pause over the bank holiday weekend.