Farage was taken to hospital with non life-threatening injuries following the crash of his two-seater aircraft at Hinton-in-the-Hedge airfield, near Brackley in Northamptonshire.
Britons are voting in the most-keenly fought general elections. Farage is contesting against Bercow in Buckingham in today's elections.
Witnesses saw him walking out of the aircraft covered in blood. His agent, Chris Adams, said: "Farage has been drifting in and out of consciousness and is now being X-rayed. Nigel was unconscious but he can talk."
The light aircraft was pulling a UKIP banner and it is believed it may have been caught up in the engine. The banner carried the slogan "Vote for your country-Vote UKIP".
Police said the plane went down just after 8am, also injuring the pilot, who reportedly had to be cut out the cockpit and was taken to Walsgrave Hospital in Coventry.
The pilot was seriously hurt with back injuries. Farage was taken to Horton General Hospital in Banbury.
A UKIP spokesman said: "We've had unconfirmed reports that either the banner got snagged up or there were cross-winds and it was unfamiliar airfield to the pilot, who had to be cut out of the plane.
"UKIP is sure that everybody involved in today's General Election will join us in hoping and praying that the pilot recovers from his injuries as soon as possible."
Farage suffered "minor head injuries" but campaigners had been told to "carry on", he said.
The aircraft was believed to be a 1960s-style biplane which left the Winchester area early today and flew into Hinton.The accident happened as it was taking off again from Hinton, the spokesman said.
A Northamptonshire Police spokesman said: "Just after 8am a two-seater light aircraft came down at Hinton in the Hedges airfield near Brackley in Northamptonshire.
"Two people were on board the aircraft, pilot and passenger, and both suffered what are believed to be minor injuries."
The plane was due to fly over the counties of Buckinghamshire, Oxfordshire and Northamptionshire. The crash is being investigated by the Air Accidents Investigation Branch supported by Northamptonshire Police. TV footage showed extensive wreckage to the fixed wing plane which lay upside down in field 20m from the airstrip.
