Liberal Party figures have snubbed a Senate inquiry into the controversial Free Enterprise Foundation and similar federal fundraising bodies, while star witness Arthur Sinodinos has yet to confirm his attendance.

It is understood former Liberal fundraiser Paul Nicolaou, former NSW party director Mark Neeham, former federal director Brian Loughnane and NSW finance director Simon McInnes were invited to give evidence, but declined.

Senator Sinodinos, who is cabinet secretary, has been specifically directed by the Senate to appear to answer questions, but was listed as unconfirmed on a program posted by the committee on Tuesday.

The inquiry was prompted by a NSW Electoral Commission statement last month that the Liberals used the Free Enterprise Foundation – an "associated entity" linked to the party – to "channel and disguise" donations, including from banned donors, before the 2011 NSW election.