Demonstrators will stage a protest outside the annual meeting of HSBC on Friday to call for better regulation of the banking sector.
Activists from the Robin Hood Tax group will dress as bankers and will carry a washbasin filled with fake £50 notes outside the venue in Westminster.
David Hillman, spokesman for the campaign, said: "We urge the next government to do more to fix the financial sector.
"Greater scrutiny of the city will help banks clean up their act.
"A Robin Hood Tax would provide greater oversight of the markets and raise billions for public services and the fight against poverty.
"Nearly a decade after the financial crisis the banks caused, not enough has been done to rein in the bad behaviour of large finance firms."
The campaign is a coalition of 119 organisations, including Unison, Barnardo's, Comic Relief and Oxfam.