Oracle has accused Hewlett-Packard of fraud for concealing facts during negotiations between the two companies, according to a court filing.
The cross complaint filed by Oracle against HP on Tuesday is the latest salvo in ongoing litigation over the Itanium platform.
Oracle decided in March to discontinue its support for Itanium, a heavy-duty computing microprocessor, saying Intel made it clear the chip was nearing the end of its life and the company's focus was on its x86 microprocessor.
HP has dubbed Oracle's decision "anti-customer" behaviour. The company sued Oracle in a California state court in June.
The litigation has been part of a deteriorating relationship between the two companies. Oracle hired former HP chief executive Mark Hurd last year after Hurd left HP amid questions about his relationship with a female contractor.
HP filed a trade secrets lawsuit against Hurd related to the Oracle hire, which was soon settled.
In the filing on Tuesday, Oracle claims HP fraudulently induced Oracle to enter into the Hurd settlement.
HP concealed the fact it was about to hire Leo Apotheker as its chief executive and Ray Lane as its chairman, Oracle's filing says.
Apotheker and Oracle CEO Larry Ellison have long been rivals from the time Apotheker headed European software maker SAP. HP Chairman Ray Lane and Ellison had a troubled relationship from the time Lane was fired from Oracle in 2000, according to the filing.
"Given the well-documented animosity between Oracle and Messrs. Apotheker and Lane, HP knew that Oracle would not have signed the Hurd Agreement had it known of HP's imminent plans," the filing says.
HP spokeswoman Mylene Mangalindan said HP is resolved to enforcing Oracle's commitments to HP and to their shared customers.
"Rather than focusing on what is right for our joint customers, Oracle is relying on invented excuses to cover up its blatant disregard for its legal obligations," Mangalindan said in an email.
Other claims asserted by Oracle against HP include defamation and intentional interference with contractual relations. Oracle seeks rescission of the Hurd agreement, general and punitive damages and other remedies.
The case in the Superior Court of the State of California, County of Santa Clara is Hewlett-Packard Company v. Oracle Corporation, No. 11CV203163.
(Reporting by Dan Levine; editing by Tim Dobbyn and Andre Grenon)