Dave says he will not go into coalition after the election:

“The Prime Minister wants to make a commitment in the Conservative Party election manifesto not to sign a second power-sharing deal with a smaller party in the event of a hung parliament next May, it is understood.”

No.10 are not denying the story, instead saying that the PM is in it to win it. 

Such a promise reminds Guido of a remarkably accurate election broadcast from the Tories just before the last election. Who remembers The Hung Parliament Party? The broadcast went out while the Tories prepared for a Con/Lib government:

Is that a ‘cast-iron guarantee’ Prime Minister?