"Once we close the inquiry and publish the report, we will look to spread any wider learning points that may emerge into the sector," a commission spokeswoman told Third Sector.
The regulator's preliminary investigation has focused on seminars that the institute held at 11 Downing Street, as well as its senior research programme and educational work.
A spokesman for IPPR, a left-leaning think tank that is also a charity, said that think tanks should be able to continue their work without compromising their charitable objectives.
"We are independent and non-partisan and will work with any organisation or political party to exchange ideas and develop policy that will further our aims," he said. "We are driven by our values, not by affiliations to any party or interest group."