Philip Davies, MP for Shipley in West Yorkshire, told Third Sector he doubted the credentials of Common Purpose, an education charity that runs leadership courses, often attended by senior public servants, for as much as £5,000.
Davies, a strong Eurosceptic, said the organisation acted as a high-level networking arena for the public sector, and he did not think this was a charitable purpose.
Common Purpose got an "astronomical amount of support" from the taxpayer, he said, through free use of office space in public buildings, including the Sheffield office of the Department for Children, Schools and Families. "Lots of worthwhile charities don't get a sniff of this support," he said.
Roger Helmer, Conservative MEP for the East Midlands, also a Eurosceptic, told Third Sector he also had concerns about Common Purpose's charitable status: "It seems to me that it operates largely as a commercial training organisation, and, beyond that, as a lobby group promoting an unthinking acceptance of the rightness of the EU."
A spokeswoman for Common Purpose said: "It's a very common practice for charities to receive pro-bono use of spare office space in all sorts of organisations.
"Common Purpose has office-hosting arrangements with a whole variety of organisations from all sectors on individually negotiated terms.
"We seek sponsorship to offer bursary places to people who may otherwise not be able to attend a programme, and for audiences that cannot pay fees."
Common Purpose said Davies had been supportive of the organisation in the past and had hosted an event in Shipley in 2006.
A Charity Commission spokeswoman said the regulator would write to Davies to address his concerns. "Charities can charge fees that more than cover the cost of services or facilities, provided that the charges are reasonable and necessary to carry out the charity's aims," she said.