The farmers launched a one day action at Immingham Dock in a protest designed to highlight the plight of the UK pig industry which they say is close to financial ruin.
The demonstration targeted lorries from Denmark, one of the main suppliers of pork products to Britain's supermarkets. Danish pig farmers use the cheaper "stall and tether" rearing method, a practice which is banned in the UK from next January, allowing them to undercut their British rivals.
The protest passed off peacefully with no arrests, according to Humberside Police, and disruption to port business was minimal.
An estimated 800 farmers, some arriving on tractors and muck-spreaders, carried placards and waved banners.
Lorry drivers entering the port were stopped, given pork sandwiches, and told the harm importing pig meat is doing to livelihoods.
The action marks a stepping up of the campaign to raise the profile of the British pig industry which has been overshadowed by the BSE beef crisis. Campaigners say the pig industry is losing some pounds 200m a year through depressed prices and a flood of cheap imports as wholesalers take advantage of the strong pound to buy more pork from abroad.
The industry faces further problems from new legislation which outlaws the "sow stall" in the new year.
The "sow stall" is the pig equivalent of the veal crate, a metal cage 8ft by 2ft which is large enough for an adult pig to stand in but not turn around. Farmers are now returning to traditional, and more costly, rearing methods which allow pigs to roam in 25 sq ft pens.
The ban was brought in following pressure from the RSPCA, consumers and animal welfare campaigners but does not apply to the Continent nor does it prohibit British wholesalers importing animals reared in factory conditions.
The return to more humane methods has cost an estimated pounds 500 per pig leaving the average-sized pig farm with a bill of around pounds 150,000.
Digby Scott, spokesman for the British Pig Support Group, said: "The situation for a large number of farmers is desperate. Prices for British meat have slumped to their lowest level in 60 years and many farmers are having to quit the business. Farmers have cried wolf in the past but the industry this time is at crisis point.
"Shoppers have told us they want British pork and bacon because it is safer and better, so why won't the supermarkets sell it?"
Supermarkets insisted they always tried to buy British.
Sainsbury's said 100 per cent of pre-packed pork was from the UK, but only 50 per cent of its bacon was British. Tesco and Safeway said they would only buy from farms where "sow stalls" were not used.
Asda said 90 per cent of its fresh pork was British but it did buy in French loin pork because of short domestic supply.