The bank, which spent £12 million in 2005, according to Nielsen Media Research, uses Media Planning Group to handle planning and buying.
MPG has held the account since ING Direct launched in 2003, backed with £25 million in marketing support.
The AAR is handling the review process and MPG will repitch for the account.
Gina Fusco, the sales and marketing director at ING Direct, said: "Now that we have passed the important one million-customer milestone and new products are on the horizon, it is appropriate and best practice to review our current media handling arrangements."
Marc Mendoza, the MPG managing partner, said: "We are looking forward to continuing a successful relationship and fully understand that a financial services company that has now reached this size would want to undertake a benchmarking exercise."
ING Direct's creative account will continue to be handled by VCCP.
ING Direct, a division of the Dutch banking group ING, has 15 million customers worldwide.
- Media Perspective, page 10.