The number of new patent infringement lawsuits in the US rose more than 10 per cent to 6,092 last year despite a 2011 law specifically aimed at reducing patent litigation, according to the analytics group Lex Machina.
The number of actions last year increased 12.4 per cent from 2012 despite the America Invents Act (AIA), which was the most significant overhaul of the patent system in decades.
"If the AIA's intention was to make the patent litigation system predictable and less expensive, it hasn't met those goals yet," said Owen Byrd, lawyer for Lex Machina, which collects and interprets data on patent litigation.
Byrd and Lex Machina chief executive Josh Becker said they believed that the total was a record for infringement actions.
The United States Congress is trying again to make changes to the patent system to reduce frivolous litigation, but progress seems to have stalled after a bill was passed in December.
The Lex Machina study found companies such as Apple, Amazon.com  AT&T and Google were the most likely to be sued.
The 10 most active plaintiffs were patent assertion entities, which critics disparagingly call patent trolls because they make their money from legal actions and licensing instead of manufacturing.
The top three were Melvino and ArrivalStar; Wyncomm; and Thermolife International. Each filed more than 100 infringement actions, Lex Machina found.
A Texas court continued to attract the most traffic, with 1,495 infringement cases filed there last year, a 20 per cent increase over 2012, according to the study.
A single judge in the state's eastern district had more than 900 cases last year, Lex Machina found.
Companies usually file infringement lawsuits in district courts to win monetary damages and often file a second lawsuit at the US government's International Trade Commission (ITC), which can block infringing products from the US market.
The ITC had seen a big spike in cases filed in 2011, to 70. But the number has fallen to 42 new cases in 2012 and 41 last year.