She said that she would talk to those involved but would stop short of calling the police.
The views of Thornberry, the MP for Islington South and Finsbury, contrast with those of Priti Patel who said she would not hesitate to inform on rule breakers.
Asked on Sky’s Sophie Ridge on Sunday programme whether if she knew her neighbours were breaking lockdown rules she would call the police, Ms Thornberry said: “No, but I would talk to them about it.”
Previously asked if she would report on anyone braking the Rule of Six Patel replied: “Quite frankly I would call the police.”
Thornberry also defended staying in former Labour leader Jeremy Corbyn’s cabinet despite anti-Semitism allegations.
Asked why she stayed in Mr Corbyn’s shadow cabinet she said: “Because I felt that it was a struggle, but that we were going in the right direction.
“So that … processes had taken too long to improve, but they were getting better.
“I didn’t know the extent of the issues in terms of the interference of Jeremy’s office with the disciplinary process, I didn’t know the extent of that because, obviously, I’m not on the NEC, I’m not involved in the background stuff.
“I knew that we were making progress. It was a struggle, but it was the right place for me to be, was to be there making sure that we were going in the right direction.”