Roger Whiteside, Threshers' chief executive, said the decision followed a strategic review of the business, but sources close to the group claimed the returns had failed to justify the cost of retaining membership.
Whiteside added that the group, which also owns The Local and Wine Rack chains, wants to focus more on in-store experience, including emphasising its range and discount deals such as three for the price of two.
A Nectar spokeswoman confirmed that Threshers was leaving the scheme; it would not say whether it would seek to replace it with another off-licence chain.
Threshers is one of Nectar's longest-standing members, having joined shortly after its launch in 2002. Only Sainsbury's, Debenhams and BP, all of which were founder members, have been with the scheme longer.
The most recent brand to leave Nectar was Vodafone, which ended its two-year tie-up with the scheme to focus its reward strategy on offering customers cheaper calls (Marketing, 13 July 2005).
At the time, industry insiders speculated that the operator did not feel its status as a points collection partner offered it enough value.
Nectar recently revamped its marketing strategy for the first time since launch. Earlier this month it created an ad campaign featuring a series of characters called The Nectars. The decision followed customer research indicating that its campaigns needed more warmth and humour.