Tim Montgomerie, who was Iain Duncan Smith's chief of staff during his final months as party leader in 2003, set up the ConservativeHome website in 2006.
The site says it aims to "champion grass-roots party members and advocate a balanced, authentic conservatism". Former shadow third sector minister Greg Clark describes it as a "must-visit site for Conservatives today".
Now ConservativeHome has established a Left Watch blog, co-edited by Montgomerie and Jonathan Isaby, a former political writer for The Daily Telegraph.
The blog's first entry last month accused Katherine Rake, chief executive of the Family & Parenting Institute, and Ben Summerskill, chief executive of gay rights charity Stonewall, of using their positions to "bash the Tories".
Its second blog, headlined "We need a list of taxpayer-funded charities that should lose their welfare cheques", says: "One of the first acts of any Tory government should be to end government funding of all charities with a political agenda."
It adds: "Summerskill's political ranting against the Conservatives shouldn't continue at all our expense."
A Conservative Party spokeswoman said ConservativeHome was not affiliated to the party and did not reflect the party's views.
Nick Hurd, shadow third sector minister, said: "Bloggers are free to express whatever opinions they want. They should not be interpreted as party policy."
Summerskill, a former Labour Party member, described the attack on his organisation as "sinister and inept". Stonewall, he said, received "little more than a tenth" of its income, and no core funding, from statutory sources.
"Whatever government is in office, it is our thousands of donors who will be the guarantors of our independence," he said. "I hope the Conservative front benches will robustly distance themselves from what appears to be an attack on the charity sector."
The Family and Parenting Institute receives 93 per cent of its funding from statutory sources. Rake said: "Our views are based on policy, research and evidence."
Montgomerie did not respond to inquiries from Third Sector.