A Metropolitan Police officer committed gross misconduct when he restrained a photographer at a rally for Labour leader Jeremy Corbyn in north Wales, a disciplinary panel has found.
PC Mark Dawson has been given a final written warning over his actions in Colwyn Bay, Conwy county, in June 2017, the day before the general election.
PC Dawson was assigned to a specialist protection group at the time.
The photographer suffered minor injuries, the panel was told.
The ruling against PC Dawson was published on Tuesday on the website of the Independent Office for Police Conduct (IOPC).
It said the independent panel decided PC Dawson breached the standards of professional behaviour.
The press had been trying to follow Mr Corbyn from a stage through a gap to the promenade in Colwyn Bay when the photographer was restrained on the ground, the panel was told.
The IOPC examined videos and photographs and took eye-witness testimony from journalists, police officers and stewards.
The incident was also referred to the Crown Prosecution Service which decided against bringing criminal charges.
IOPC regional director Jonathan Green said it was "important for public confidence" that the case was independently investigated as it occurred in public view at a "pressured environment", the day before the election when the "threat to any party political event would be considered high".
"Police use of force must be proportionate, necessary, and reasonable and the individual officer must be able to justify it," he said.
"Our investigation concluded the officer's actions could be considered disproportionate.
"A panel has now ruled that PC Dawson was in breach of professional standards and he has been given a final written warning."