The defection of a Conservative councillor to Ukip is a "huge blow for David Cameron's authority", Labour has said.
The party's shadow minister without portfolio, Jon Trickett, said the move showed even the Prime Minister's candidates "know he cannot win a majority".
"Ukip and the Tories increasingly share the same people as well as the same policies," he said.
"Both stand for increased health service privatisation, extreme spending plans which threaten the NHS and further tax breaks for those at the top."
“David Cameron will not rule out working with UKIP, but this is clearly what his party wants. David Cameron must now come clean and tell us what his plans are to do a deal with Nigel Farage and UKIP.”
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