Miliband mispeaks - is there a word for this?

In an interview on Monday, Ed Miliband used the phrase "shuffling the deckchairs". This is a conflation of two phrases. "Shuffling the deck", a dead metaphor originally from playing cards of course, but now just meaning "changing things about". It is usually used to describe an attempt to refresh a situation, and is therefore a mildly positive action, a first response to a not so serious situation. "Re-arranging the deckchairs on the Titanic" on the other hand is negative, futile activity - defined online as "saying that someone is wasting time dealing with things that are not important, and is ignoring a much more serious problem". (Bit of an understatement). Interestingly, this phrase seems only to have gained currency in the late 1960's.

I think it is obvious what happened here - Miliband's brain suggested to him the original phrase - shuffling the deck - but he realised halfway through that it wasn't quite what he intended to say, so he changed tack (dead metaphor alert) adding the "chairs" suffix, leaving him with a neither Arthur or Martha phrase. Was it just me, or was there a quick flash of puzzlement in his eyes as he said it - "did I get that right, it didn't sound quite right?". The second phrase obviously was suggested by the coincidence of "deck" and "deckchairs", and interestingly Miliband isn't the first to have done this - the online Urban dictionary gives some other examples of the use of the phrase, although doesn't acknowledge its complex origins.

This happens all the time - people misremember or misunderstand phrases or idioms, and create new ones in the process. This undoubtedly happens with individual words, the best example being meld quoted by Stephen Fry on QI a few years back. "Meld", by its similarities to both "mix" and "weld", came to be used to mean (and then to mean itself) "combine", despite its original meaning being very different. Examples of new idioms being coined by the accidental collision of old ones are rarer, but I haven't been able to find a word for this - is there one?

Incidentally, these only work if they are accidental, where the associations between phrases are allowed to float to the surface of someone's consciousness - trying to force them doesn't work e.g. "Don't put all your eggs in one basket before they hatch". See what I mean?