The Second Source, an alternative professional network, launched on Thursday night with the aim of raising awareness of harassment and helping companies to stamp it out.
It has the support of London Mayor Sadiq Khan, Green MP Caroline Lucas and the Lib Dems’ Jo Swinson.
It comes in the wake of allegations Times columnist Kate Maltby and radio presenter Julia Hartley Brewer faced sexual harassment from male MPs.
Evening Standard columnist Rosamund Urwin, who is among the 20 journalists behind Second Source, said she was inspired to take action after hearing how freelance reporter Emily Reynolds was targeted.
She said: “It was after reading a piece by my fellow journalist Emily Reynolds about sexual harassment she had suffered that I realised that unless we act, nothing will change.
“It will happen to the 23-year-olds of tomorrow, as it once happened to me and happened to Emily.”