Unite staged two protests on Saturday in a bid to help save the Agricultural Wages Board (AWB).
Union members gathered outside posh London hotel the Savoy in the Strand to protest at the Fresh Produce Consortium annual dinner being held there.
The action followed a gathering of union activists outside the Somerset constituency of Liberal Democrat Agriculture Minister David Heath, who is responsible for driving through the proposed abolition of the AWB after having previously supported it.
Unite national officer for agriculture Julia Long said: "The campaign has gained great momentum recently and this weekend's protests are aimed at driving home the message that agricultural workers won't have their incomes reduced to poverty levels.
"David Heath has reneged on his previous position of supporting the AWB to do the bidding of the major supermarkets whose executives will be living it up at the Savoy, as they discuss how to impoverish those working on the land in all weathers."
Foreign Minister Alistair Burt's admission that the Cameron government has "supported" a survey of attitudes to US drone strikes in Pakistan's tribal areas amounts to a tacit admission of British involvement.