TUC general secretary John Monks and London Mayor Ken Livingstone gave out leaflets to City workers last week, urging them to join a trade union to secure their employment rights.
Unions in London are running an 'Organise the City' campaign to raise awareness of employment rights and increase the profile of trade unions in the City.
Volunteers have given out thousands of advice leaflets to workers at train stations and targeted workplaces.
Unions claim that bullying and harassment, discrimination, stress, excessive working hours, wrongly handled redundancies, unequal pay and wrongful deductions from pay are rife in the City.
Monks said: "The businesses that are successful in the long-term are those that practice justice, fairness and respect in the workplace. "It is no accident that 42 of the top 50 FT companies work closely with trade unions."
Livingstone said he supported the campaign because it would help encourage City employers to offer world class terms and conditions of employment. "Our objective must be quality employment rights," he said.
"I urge every employer in the City to work closely with trade unions to promote efficiency, safety and fairness at work."