A number of anti-capitalism protesters have been arrested by police after gathering outside London's Guildhall during the Lord Mayor's Banquet, according to campaigners from Occupy London.

They said seven members of the campaign group, which has been camped on the doorstep of St. Paul's Cathedral for the past month, were held by officers on Monday evening following a demonstration at the City of London Corporation's headquarters.

Prime Minister David Cameron was attending the annual banquet along with a number of other dignitaries at the time of the protest.

Demonstrators, who donned dinner jackets, floor-length dresses and pig masks, described the banquet as a "symbolic event of the rich and powerful."

Following the arrests, a number of Occupy London supporters congregated outside Bishopsgate Police Station where the detained protesters were taken.

They claimed they tried to enter the station but were restrained by officers who used "physical force" against them.

"Around 16 of us went outside the station and told the police we wanted to wait for our friends but they wouldn't let us in the lobby and were pushing us away. One protester ended up breaking their finger," protester Nafeesa Shamsuddin said.

Occupy London member Louise Hutchins, 31, from London, said the original protest outside the banquet was "against the extreme concentration of wealth and power which is represented at the Guildhall."

"This event is the symbolic event of the rich and powerful, the 1%," she added.

"We question whether they should be having such a luxurious banquet in a time of austerity," another protester, John Sinha said.