* Leighton asks Australia's Takeover Panel to block bid
* ACS reiterates no plan to change management at Leighton
* Hochtief CFO says talks with Qatar could be possible
* Hochtief shares up 2.4 percent at 64.94 euros
* DAX index up 0.6 percent
(Adds CFO comments, specifies value of deal, update share price)
MADRID/MELBOURNE, Oct 25 (Reuters) - Leighton Holdings, the Australian affiliate of German construction firm Hochtief, has asked Australia's Takeovers Panel to help it fend off a bid for its parent by Spain's ACS.
Leighton said on Monday it wanted the Takeovers Panel to declare "unacceptable circumstances" in ACS's bid for Hochtief, as it was worried that ACS was trying to take control of it through a cheap offer for Hochtief, avoiding a fully priced takeover offer for Leighton.
Hochtief, which controls Leighton, failed in its first attempt to use Australian regulators to thwart ACS's low-ball bid, as the Australian Securities and Investments Commission declined to force ACS to make a takeover bid for Leighton.
ACS has said it would offer Hochtief shareholders eight ACS shares for every five Hochtief shares they own. At current prices, the proposed deal values Hochtief at 4.24 billion euros ($5.95 billion), a 7 percent discount to its market value.
Hochtief is hoping that the Australian Takeovers Panel will be more supportive to its plans to fend off ACS's bid, though lawyers said it was unlikely that the regulator would force ACS to make a full bid for Leighton.
ACS reiterated on Monday that it had no plans to change management at Leighton if it won control of Hochtief.
In another defensive move, Hochtief's Chief Executive Herbert Luetkestratkoetter met with Qatar's Economy Minister Youssef Kamal at the end of September, lobbying for support against the ACS offer.
In an interview with Reuters TV, Hochtief's Chief Financial Officer Burkhard Lohr did not comment directly on the possibility of Hochtief seeking support from Qatar to fend of the attack, but said that Hochtief has many projects in Qatar, and that it was therefore possible to "discuss other topics".
Lohr also said that if ACS were to take over the majority of Hochtief, there would be many shareholders who would not consider giving their shares to ACS.
"Even in the current situation there are plenty of investors who are interested in increasing their share or investing anew," Lohr said.
Hochtief's shares were up 2.4 percent at 64.94 euros by 1326 GMT, outperforming the XETRA DAX index, which was up 0.6 percent. (Reporting by Sonali Paul in Melbourne, Josie Cox in Frankfurt and Rene Wagner in Berlin; writing by Jonathan Gleave; Editing by Sharon Lindores) ($1=.7124 Euro)