LONDON (Reuters) - Forget the opinion polls and betting odds, one English farmer has his own way of predicting the outcome of Britain's looming referendum on whether to stay in the European Union or leave - racing his miniature pigs.

The pigs of Pennywell Farm in Devon successfully predicted the outcome of Britain's national election last year and are again fighting it out on the track in some political racing that rival the "Remain" and "Leave" sides' own campaign battles.

Prime Minister David Cameron is leading the "In" campaign and former London mayor Boris Johnson, also from the ruling Conservative Party, is urging Britons to vote "Out" in the June 23 referendum.

As the latest polls show growing momentum for the "Leave" camp, the farm in southwest England is putting four pigs to the test each afternoon on a 150 yard (137m) long course, with both sides represented.

Racing for the "Remain" camp are 'David Hameron' and 'George Hogsborne', a play on the name of finance minister George Osborne. For the "Leave" camp the racers are 'Boar-is Johnson' and 'Iain Duncan Sniff', a reference to leading Eurosceptic and Conservative ex-cabinet minister Iain Duncan Smith.

Monday kicked off the farm's first "referendum race" despite dense fog hanging over the track.

"I think this is most appropriate weather for this occasion," Pennywell Farm owner Chris Murray said.

"It's a murky question, we are all in the fog about it and I think that these little Pennywell miniature pigs will actually find a way through this fog of confusion and indecisiveness."

The track features jumps named "Bacon Brook" and "The Trough", leading to the finish that consists of two Union Jack and EU-themed gates.

Once the starting gate was opened, spectators cheered as David Hameron, George Hogsborne and Iain Duncan Sniff rushed off, easily clearing the hurdles, while Boar-is Johnson trailed behind. The result in the end was decisive. 

    "We've had three votes for staying in the EU and just one for leaving," the race compere announced.

Pennywell Farm will conduct the races daily up until the vote.

(Reporting By Reuters Television; Writing by Georgina Cooper and Marie-Louise Gumuchian; Editing by Gareth Jones)