But the organisations deny that they are "paying for a say in Parliament" and claim the practice is "part of the democratic process".
The Skin Care Campaign and the RNID were revealed in The Times last week to be paying £15,000 and £6,000 a year respectively to separate all-party Parliamentary groups. But Third Sector has learnt that many more charities offer either annual sums or administrative support to such groups.
The funds are mainly used for secretariats or research work.
The NCVO donates £10,000 a year to the group that deals with the community and voluntary sector, and the Barrow Cadbury Trust gives £24,000 to the human rights group.
Housing Justice used a £20,000 grant from the Joseph Rowntree Foundation to fund the group on homelessness and housing need.
Peter Lapsley, chief executive of the Skin Care Campaign, said: "There is nothing wrong with external organisations representing a group of patients seeking to influence Parliament - it is part of the democratic process."
Mark Morris, head of Parliamentary and European affairs at the RNID, also defended his charity's contribution.
"There is nothing underhand about this," said Morris. "No MP gets money for being a member of this group."
Pete Moorey, Parliamentary and campaigns officer at the NCVO, said: "It is not a case of the sector paying its way.
"The group you are supporting is not your group, it's the members' group."
But Sir Alistair Graham, chairman of the Committee on Standards in Public Life, has suggested the practice could begin to "dominate" policy.
He told the BBC that providing the secretariat and research work "may, perhaps, not immediately, but over a period of time, influence policy".