British Deputy Prime Minister Nick Clegg on Monday condemned the riots in London over the weekend, calling the rioting as "needless opportunistic theft and violence."

"It is completely unacceptable and the people who have suffered are those who have lost their businesses, shopkeepers who have lost their shops, families who have lost their homes and many people who felt very frightened in their own neighbourhoods," Clegg said.

The government stood "side by side" with the victims in utterly condemning the rioting and looting, he said, adding that there should be no excuse whatsoever for creating feelings of insecurity.

Clegg said the rioting had absolutely nothing to do with the death of 29-year-old Mark Duggan, which was quoted in earlier media reports as the cause for the weekend violence.

The weekend violence erupted Saturday at Tottenham after a peaceful demonstration degenerated into a smashing and looting rampage. Police said on Monday that more than 100 people had been arrested in connection to the violence.

Meanwhile, the Deputy Prime Minister dismissed the notion that the government failed to function effectively following the riots.

"We are working effectively together as a team this week as we do every week of the year," he said.

A spokesman for British Prime Minister David Cameron, holidaying in Italy, said Cameron was in constant contact with officials during the riots.

Home Secretary Theresa May also ended her summer holiday and is expected return to London on Monday afternoon to meet with metropolitan police.

"Londoners have made clear that there are no excuses for violence, and I call on all members of local communities to work constructively with the police to help them bring these criminals to justice," earlier reports quoted May as saying.