The ad, by The Walker Agency, was broadcast over a two-week period earlier this year, and offered cash-strapped consumers a loan in exchange for temporary possession of their valuable goods.
A voiceover stated: "If you need money in a hurry you could always sell your valuables. Trouble is, it's not the best time to sell and once they're gone, they're gone. So why not visit borro.com? We could look after your valuables and transfer you a lump sum and when you repay your loan she'll get everything back."
One viewer complained that the ad was misleading because it did not state there was substantial interest to pay on the loans.
Borro.com, which launched last summer with the aim of targeting middle-class consumers struggling in the recession, said guidance from legal advisers and Clearcast had suggested it need not state an annual percentage rate (APR).
However, the ASA concluded that the phrase "need money in a hurry" constituted an incentive to obtain credit, and therefore according to Office of Fair Trading (OFT) regulations was required to provide a typical APR.
The ad must not appear again in its current format.