Aid organisations said migrants camped in Calais had made last-ditch attempts to cross the Channel ahead of today's operation.
Border police were said to have spotted groups of up to 40 people hiding in bushes along roads leading to the port.
Some were attempting to jump on lorries as they slowed down.
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The PM promises to double to 200,000 the number of homes built under an existing scheme aimed at easing Britain's housing shortage.
The Met Office has weather warnings in place for snow and ice until 10am in the north and west.
The plan, which would effectively strip banks of the benefit of recent corporation tax cuts, forms part of the party's election manifesto.