Police have launched an investigation after a brick was thrown through the window of the office of Wakefield MP Mary Creagh.
The Labour MP took to Twitter to condemn the attack, which she said had left staff "distressed".
West Yorkshire Police said they were called to the office, on Cheapside in Wakefield, following the incident.
A force spokesman said the building was empty at the time the brick was thrown.
Tweeting about the attack on her constituency office, Ms Creagh said: "Staff distressed to discover brick through office window in Wakefield this morning. No excuse for violence and intimidation in our democracy."
The police spokesman said: "Police were called to an address on Cheapside in Wakefield at 12.50pm today, following reports that a brick had been thrown through a window.
"The building was unoccupied at the time.
"Inquiries are ongoing to determine the circumstances surrounding the incident."
Anyone with information is asked to contact police on 101, quoting 725 of September 12.