I don't agree with that at all. I think the Tories do certainly. And there are people in the Labour party who do too, but not to the same significant level. As for the Lib Dems, you were massively clutching at straws when you mentioned them earlier just as you are now - they are an openly PRO European party. You don't vote for them at all if you are inclined to get out of the EU. They have their own problems of vote desertion and I would guess no more than 2% at the door of UKIP.The reason they are getting the level of publicity they are is because all three main parties feel threatened by UKIP. It also helps that foaming mouthed lefties can't help holding protests etc.
But the simple fact is that UKIP are a single issue party, and the issue is very debatable and contencious for a variety of reasons.