Formula One commercial boss Bernie Ecclestone said on Tuesday he had turned down an approach to take over the sport's holding company, Slec.
Ecclestone is trying to secure the future of F1 beyond 2007
Ecclestone said in a statement that he had been approached with an unspecified buy-out offer but that "the company shares are not for sale".
The statement did not give any details about the potential investor.
It comes on the eve of a meeting on 31 August between F1's teams, owners and governors over the future of the sport.
The major car makers have threatened to set up a rival championship after 2007, when the existing deal tying the teams to F1 ends, if they are not given a greater share in its revenues and greater transparency.
They are meeting with the teams and Max Mosley, president of F1's governing body the FIA, in Milan on Wednesday to discuss plans for a compromise deal that will keep the sport together.
So far only three teams, world champions Ferrari and privately-owned Red Bull and Jordan have agreed to extend the existing "Concorde Agreement" to 2012.
The other teams - many of them owned or part-owned by car manufacturers - are pressing for a better commercial deal.
The motor manufacturers in F1 want a better financial deal
Slec is 75% by the banks Bayerische Landesbank,
JP Morgan and Lehman Brothers, with Ecclestone's family trust
controlling the remainder.
Ecclestone has previously been dismissive of the banks' interest in F1, insisting they were only in it for the money.
But Tuesday's statement contradicted this view, saying: "The shareholders are long term investors and have the interest and stability of Formula One foremost in their mind."
A number of potential investors have been mooted in recent weeks.
The Sunday Telegraph newspaper reported at the weekend
that financier Robin Saunders was planning a $1.5bn (£840m) purchase of F1 through a private equity firm and had held extensive negotiations with Ecclestone.
It said Saunders planned a leveraged buy-out of the sport in
a scheme that would eventually see the teams owning the
The Business newspaper reported at the weekend that BSkyB
chief executive James Murdoch had told a consortium of US and
British private equity firms that he was open to playing a role
in any F1 bid.
Another reportedly interested is Hong Kong-based conglomerate Hutchison Whampoa's Tom Group, who said last month it was premature to say it was in talks on a specific deal.