Darling said the leprechauns were sneaking into savers' bedrooms in the early hours, climbing onto their pillow and promising to hide their gold under an old rowan tree.
But, he insists, the leprechauns have a secret plan to bury the gold and then refuse reveal its location, keeping it all for themselves to spend on bottles of stout and mutton pies.
Darling said: "They're about four inches high and are dressed in a fine tunic and breeks, a pair of shiny boots and a tall hat.
"They carry a little purse filled with magic dust and can make themselves invisible, which is of course illegal under European competition rules."
Mr Darling said if you spot a leprechaun you must keep your eye fixed on them at all the times 'otherwise they'll disappear'. He added: "There's one in here right now. I can sense him."
The chancellor is urging savers to keep a medium-sized jar next to the bed, so the leprechauns can be captured, flown back to Ireland and released in a meadow.
But Declan O'Flaherty, Chief Gold Keeper of the Kilkenny Little People, said: "Come now, give us yer gold. I've picked out a beeotiful, magical tree with an AER of 4.5%.
My sisters little boy friend is a leprechaun. He talks the nice talk, takes things that don't belong to him and lies about it. I keep tellin the wee person my sisters a nut case and he, the wee leprechaun should forget about her. He than exclaims, but I can help her.
Them wee leprechauns, are a funny bunch. That is, as long as there's something of value to hold there interest.