The Big Issue magazine is to be sold by the unemployed and not just the homeless.
The weekly publication, which will celebrate its 20th anniversary in September, has changed the rules due to the tough economic climate.
Founder John Bird said the point of the magazine was to help people in a crisis which included some of the unemployed.
But some vendors have raised concerns the change will dilute the charity's message.
"We're now meeting people that would never have come to the Big Issue, professional people, former solicitors for example," Mr Bird told BBC London.
'Here to help'
"And we're saying we're here to help people, anybody in a crisis.
"We don't want to see people slip into long-term unemployment and homelessness."
London vender Mahesh Pherwani, said: "I do not see it as competition - we are all in the same boat.
"But it will have an impact on people's perception of how the Big Issue operates and what it exactly represents."
The Big Issue was launched in London in 1991 with the aim of helping the homeless help themselves, and the slogan of 'offering a hand up, not a hand out'.
It operates by selling the magazine to vendors for half the cover price. They then get to keep the difference when they sell the magazine on.
Back in 1991 it cost just 50p, now it is £2.
There also are now editions in the North, the South West as well as Wales and Scotland.
The charitable organisation currently supports 2,900 people and the magazine is read by nearly 700,000 people every week.
Speaking on its impact Mr Bird said: "I think the greatest thing we've done is we've changed the way people look upon the homeless.
"We've given dignity back to the victim, so the victim can stop being a victim."