ITV News has filmed an altercation outside the home of Liberal Democrat MP Mike Hancock, earlier today.
In a statement, a Hampshire police spokesman said: "A reporter received an injury to his nose during the incident.
"Police officers attended and are conducting an investigation into the circumstances surrounding the incident.
"A 37-year-old man has been arrested on suspicion of assault, and is being taken into custody where he will be interviewed by officers today."
Mr Hancock was suspended from the party yesterday following a report on alleged sexual impropriety.
More top news
ITV Border Political Editor Peter MacMahon says it's far too early to call this referendum.
A World War Two veteran has told ITV News he has fulfilled a boyhood dream by voting for an independent Scotland.
Speaking as a Scot - not the ITV News Scotland Correspondent - I am feeling a great anxiety about what lies ahead.