Guests arrive for the private view of Bruce Nauman's Turbine Hall installation at Tate Modern on Tuesday evening were faced with a GMB picket line.
The GMB staged the demonstration outside Tate Modern as part of a campaign aimed at saving a Birds Eye factory in Grimsby which is due to close with the loss of 600 jobs.
Birds Eye owner Unilever has sponsored the programme of Turbine Hall installations since the gallery opened on Bankside in 2000.
Sandra Allen, a GMB shop steward who has worked at the Grimsby factory for 15 years, said the protesters wanted to embarrass Unilever, adding: "Our workforce has been an exemplary model of partnership with Unilver management. We have won awards for learning and skills development, revolutionised health and safety procedures and supported the company through two huge restructuring initiatives.
"Our reward will be over 600 kicks in the teeth."