Immigration minister Robert Jenrick is facing claims that he left his ministerial briefcase unattended on a train.
The Sun newspaper reported that witnesses had seen the Home Office minister leave his red box unattended for at least four minutes.
According to the report, Mr Jenrick was on a train back to his Newark constituency on Friday morning.
The paper also published pictures that it said shows the red box on a seat in a first class carriage on the train.
The minister could now face questions about whether a security breach was committed.
A spokesman for the Conservative minister told The Sun: “Mr Jenrick was working on the train throughout the journey, with his ministerial box close by at all times.
“He sat in the seat directly to the left of this misleading photo and he left the train with his locked ministerial box.”
The Home Office has also been contacted for comment.