The ex-boyfriend of former TOWIE star Ferne McCann also admitted hiding two sim cards and two USB sticks inside the medical aid while held on pre-trial remand at HMP Thameside in September.
The 25-year-old admitted one charge of possession of a prohibited item while in prison when he appeared via video link at Bromley Magistrates’ Court in London on Wednesday.
The court heard he wanted to use the phone to make private calls to Miss McCann, who was pregnant with their child at the time.
The banned items were found when a prison officer removed the rubber stopper from the bottom of the crutch during a cell search.
Collins had been using the crutch after hurting his feet trying to escape police while on the run for the acid attack at the Mangle nightclub in Dalston, east London in April.
The court heard evidence was later found on the phone of calls and messages to family and friends.
Collins’ lawyer, Audrey Mogan, said: “He did not have the phone for any sinister purpose. His partner at the time was heavily pregnant and gave birth the following November.
“He had this phone because he and his partner had been hounded by the media. He knows there was a phone in the cell but he knows the calls are recorded. Because of that he was afraid that information would get out to the media.”
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District judge Robert Hunter committed Collins’ case to Woolwich Crown Court for sentencing on a date to be fixed.
He is currently serving a 20 year sentence.