Google has accused its biggest rivals of banding together in patent battles to block it in the smartphone market.
Google chief legal officer David Drummond said that Microsoft, Apple, Oracle and "other companies" were colluding in a "hostile, organized campaign" against Android software by buying up patents, effectively imposing a "tax" on Android mobiles.
He made the comments after Google lost a bid to buy thousands of patents from bankrupt Nortel, adding that rivals snapping up the patents were increasing costs for consumers and stifling technological innovation.
"Microsoft and Apple have always been at each other's throats, so when they get into bed together you have to start wondering what's going on," Drummond said in a blog post.
He referred to "a hostile, organized campaign against Android by Microsoft, Oracle, Apple and other companies, waged through bogus patents."
Google is forging ahead in the smartphone market, but has been hampered by a lack of intellectual property in wireless telephony, which has exposed it to patent-infringement lawsuits from rivals like Oracle.
It lost out on the Nortel patents to a consortium grouping Apple, Microsoft, Research in Motion and others, which together paid $4.5bn.
Google individually had bid up to $3.4bn for those patents before teaming up with Intel, which on its own had bid up to $3.1bn, according to a source.
The Android software, now used by phone makers including HTC, Motorola and Samsung, has rapidly overtaken Nokia to become the world's most popular smartphone platform, with about a third of the market.
Google, which entered the wireless market three years ago with Android, is looking to strengthen its patent portfolio, Drummond said.
It has recently bought more than 1,000 patents from IBM and is now in talks to buy InterDigital, a key holder of wireless patents valued at more than $3bn, according to the Wall Street Journal.
The shift follows a wave of patent suits in the wireless industry, with HTC found to have infringed on two of Apple's patents by a U.S. trade panel.
Samsung has delayed the Australian launch of its latest Galaxy tablet due to a patent dispute with Apple, which says it "slavishly" copied the iPhone and iPad.
Oracle is suing Google, claiming Android infringed on Java patents that it inherited through an acquisition of Sun Microsystems in 2010.
Patent acquisitions are expected to accelerate, with IBM and Kodak often mentioned as shopping intellectual property on the market.
Apple, Microsoft and Oracle declined to comment.