Hi Bryan,
Apparently the going antonym for "Midas touch" is "reverse Midas
touch", often used in reference to a certain US politician. Not to
name names, but someone suggested "Bush tinge" could also be an
alternative.
Someone else pointed out that the Midas touch was actually a curse for
king Midas: sure, everything he touched turned to gold, but that
include food and drink and his daughter, then surmising that the
"reverse Midas touch" would have to be a good thing (though most
people assume that the journalists who use the expression mean that
anything touched turns into ... "manure").
"Abhorrent" seems like an extreme antonym for "charismatic", but maybe
that describes how some people find your Prime Minister.
Are you drafting a letter to "The Times"?
Cheers, Larry