Shadow attorney general Shami Chakrabarti has denied reports that she backed prisoners being able to keep their mobile phones.
The Labour peer added that mobiles are a problem "in malicious hands in the Palace of Westminster" as well as in the UK's prisons.
Reports in the Mail on Sunday claim Baroness Chakrabarti had opposed plans to stop prisoners using mobile phones, at a private meeting of Labour leaders.
Appearing on BBC One's The Andrew Marr Show, she denied ever saying it, saying the Mail's report was based on allegations.
She said: "I can say that is an apocryphal story.
"I tell you what, mobile phones are not just a problem in prison. They're clearly a problem in malicious hands in the Palace of Westminster."
The Mail quoted two anonymous sources in its report.
According to one source, Baroness Chakrabarti said: "This might sound naive, but I am not sure we should be doing this. We need to consider the rights of prisoners."
The Mail quoted a senior Labour insider adding: "People couldn't believe it. It sums up how out of touch the leadership is under Corbyn and his cronies."
The Government has unveiled plans to curb the use of mobile phone in prisons, which have been partly blamed for a rise in violence among inmates.