The Saturday protests came after the victory of the Conservative Party in the country's general elections earlier this week.
According to the BBC citing the Met police, four law enforcement officers and a member of police staff were injured in clashes that began after the protesters started throwing objects during the unplanned rally close to the British government headquarters and residence of the Prime Minister.
The arrests were made for offenses such as violent disorder and assault on a police officer, according to the British broadcaster.
On May 7, general elections were held in the United Kingdom. The Conservative party won the vote after securing the absolute majority of the seats in the lower house of the British parliament, the House of Commons.
The key points of the Conservative platform are the reduction of welfare funding and more responsible public spending.