Omnicom and Sir Martin Sorrell's WPP are thought to be the leading contenders for the massive HSBC account, which is worth £20 million a year above the line in the UK.
Although Lowe's creative work has been well received, HSBC wants a stronger network to meet its centralised communications needs.
Insiders also cite tensions within HSBC's US operations as a likely catalyst for the move. "HSBC is regarded as a small regional bank in the US," one source said. "The 'world's local bank' line has no resonance there and that has created problems."
HSBC chiefs are also believed to have been unsettled not only by the problems afflicting Lowe's Interpublic parent but by the switch away from the business by Nigel Gilbert, the London-based HSBC worldwide account director at Lowe. Gilbert is to take over as the president of the network's Asia-Pacific region.
Industry sources believe a pitch will take place early in the New Year but the process is complicated by the potential conflict problems such a move would throw up.
The loss of HSBC, one of its flagship accounts, would be a massive blow for Lowe.
HSBC has more than 9,500 offices in 79 countries and spends an estimated £60 million through the network.
The plan to consolidate all its business within a single holding group reflects what onlookers see as a more sophisticated view of communication now being taken by HSBC, which has emerged as a major global advertiser only during the past two years.
At the same time, Peter Stringham, HSBC's head of group marketing and the one-time president and chief executive of the Omnicom-owned BBDO Canada, has been taking a broader communications role.
WPP has had HSBC in its sights for some time, having failed to capture its international account in 1999.
Since then, the group's takeover of Cordiant has provided it with significant amounts of HSBC business that was previously handled by the Cordiant-owned Bates network in Asia.
HSBC is a vast potential prize. Besides its huge advertising spend, it also sponsors Formula 1 motor racing and the World Matchplay Golf Championship.
An HSBC spokesman said: "We have not called a review and there is no further comment to make. If and when there is any news, we will let you know."