CBS has sent off a warning letter to ABC over plans for a new reality show, warning execs at ABC that they “will be acting at their own peril if they continue to proceed" with a show that is too similar to “Big Brother,” reports EW.com’s Inside TV.

As we reported last week, ABC plans to debut a "Big Brother"-like show next month, with contestants living under the same roof and trying to outlast each other. The show, set for a June 18 debut, is called "The Glass House."

CBS’s letter reminded ABC that it CBS been the exclusive U.S. licensee of "Big Brother" since 2000.

CBS also released a statement objecting to ABC’s effort to "recruit a large humber of former staff from the show.”

"We don’t see how ABC can produce this new series without infringing on our rights," CBS said in the statement.