Dollar Thrifty has advised shareholder not to tender their shares to Hertz Global Holdings, as an offer of $72 a share undervalues the company.

The car rental organisation is presently being sought by two larger rivals, Hertz and competitor Avis.

“Given the uncertainty surrounding the length and outcome of the regulatory process as Hertz and Avis Budget work towards antitrust clearance, the board is recommending that Dollar Thrifty shareholders take no action with respect to the Hertz exchange offer at this time,” said Dollar Thrifty president Scott Thompson.

“We will be monitoring the antitrust regulatory process and other circumstances carefully, and our board will reconsider its recommendation if the situation warrants.”

Hertz and Avis have been bidding for Oklahoma-based Dollar Thrifty since April 2010.

Avis and Dollar Thrifty have been seeking US Federal Trade Commission approval for a merger since October – with the larger operator recently suggesting approval was near.

Shareholders initially rejected an offer from Hertz last year, but the company returned with an offer of $57.60 in cash and 0.8546 of a Hertz share for each Dollar Thrifty share outstanding last month.

The proposal then valued Dollar Thrifty at $72.