Campaigners calling for better working conditions for casual staff blocked a busy road junction for a demonstration.
The day of action was organised in memory of Simon Jones, 24, who died four years ago after an accident on his first day as a casual worker at Shoreham docks.
A crowd of protesters joined The Simon Jones Memorial Campaign which held the protest in Brighton as part of a national day of action against casualisation.
The protest outside employment agency Personnel Selection in West Street, Brighton, was one of a dozen demonstrations outside employment agencies across England and Wales.
Simon's parents, Anne and Chris Jones, were among the crowd at the Clock Tower, near the offices of the personnel agency, which demonstrators asked to be closed for the day as a mark of respect.
Campaigners handed out leaflets saying Personnel Selection sent Mr Jones to Shoreham Harbour where he was killed on his first day working for Euromin Ltd.
The demonstration, held on the fourth anniversary of Simon's death, called for agencies to make stricter checks on conditions at places where workers are sent.
Up to two million people in Britain are estimated to be undertaking casual labour.
Campaign spokesman Colin Chalmers said: "Demonstrations are taking place across the country against the casualisation that is making working life dangerous, insecure and deadly."
Keith Taylor, a green councillor on Brighton and Hove City Council, said: "It is time for people to speak up on this health and safety issue."
Scores of people, some in fancy dress including a dragon costume, took part in the protest. A band played and hundreds of balloons were released.
The demonstration was mostly good-natured but police moved in when crowds started to block the busy Clock Tower junction and two people were arrested.
Personnel Selection manager Peter O'Brien would not comment on the demonstration but said the agency had closed during the afternoon.
Other protests took place in Manchester, Leeds and Liverpool.
Supporters of the Simon Jones Memorial Campaign were due to continue their protest in the evening at the building industry's awards ceremony at the Grosvenor Park Hotel in London.
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