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.
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Britain and the European Commission reached agreement on a transition deal which will allow talks on the future trade relationship.