Leading pan-democrats protested yesterday about arrests linked to the July 1 march - by handing themselves in to the police.
Labour Party legislators Lee Cheuk-yan, Cyd Ho Sau-lan, Dr Fernando Cheung Chiu-hung and nine Democratic Party members went to police headquarters in Wan Chai.
They offered to "confess their crimes" and called on others to follow their example.
Their move came after five organisers of last week's prodemocracy march were arrested on Friday for "failing to comply with directions given by police" and obstructing officers. It is the first time police have taken action against the Civil Human Rights Front, which organises the largely peaceful demonstration.
The pan-democrats who went to Wan Chai had their details taken and were sent away.
They were joined by "Long Hair" Leung Kwok-hung, who was released from prison yesterday. After leaving the Lai Chi Kok detention centre, the League of Social Democrats lawmaker went straight to Wan Chai and said he felt like he was "walking into another prison".
This was a reference to claims of heavy-handed and political policing in the wake of the march. Police also detained 511 people who took part in a sit-in in Central after the rally.
Leung served four weeks in detention after being convicted of disorderly behaviour and criminal damage over the disruption of a forum to discuss the scrapping of Legislative Council by-elections in 2011.
Leung said: "I've been in detention for 26 days and I see changes taking place outside that are turning Hong Kong into a big prison."
Meanwhile, after a tumultuous week in politics, there are fears filibustering could block the approval of government initiatives by the Legislative Council's Finance Committee, which holds its last meeting before the summer recess on Friday.
Secretary for Financial Services and the Treasury Professor Chan Ka-Keung said it was "unfortunate" that many relief measures proposed by the government would have to be delayed.
Chan said about 50 government requests for funding, including those for a low-income allowance and a new hospital, were still waiting to be approved.
Leung, meanwhile, appealed to lawmakers from the five geographical constituencies to quit their seats to trigger by-elections.
He said these would form a de facto referendum in which voters could voice their support for universal suffrage without screening of candidates in the 2017 chief executive poll.
He said it would also be more convincing than the unofficial Occupy Central poll, in which 780,000 participated, as the government would be responsible for counting the votes.
Watch: "Long Hair": Legco is an arena — you are there to kill the bull