Nigel Farage has described the defection of Conservative candidate Mike Whitehead to Ukip as "another hammer blow to Tory pretensions in the north of England".
However, a Conservative Party spokesman dismissed Ukip's announcement as "cynical, misleading and utterly calculating to try and score political points".
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.”
The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.