Major whisky brand The Famous Grouse has withdrawn as the multi-million pound shirt sponsor of the Scottish rugby team, leaving the sport's governing body searching for a new backer.

The Famous Grouse had spent the past 16 years as the high-profile benefactor of the national side, pumping millions of pounds into the sport.

However, the Edrington Group, owner of the brand since 1999, announced yesterday it would be taking the name off the Scotland shirts after this year's World Cup, although it would remain involved on a lower level of sponsorship until May 2009.

Its decision is a huge blow to the Scottish Rugby Union, which had enjoyed the longest-running shirt sponsorship in the world of international rugby with Grouse.

It is believed in recent seasons that its involvement had been worth about £1m a season.

An SRU spokesman said: "The Famous Grouse and Scottish Rugby will work closely throughout the agreement to ensure a smooth and seamless transition, until such times as the new shirt sponsor is announced."

Bill Farrar, group sales and marketing director of the Edrington Group, said there were "international opportunities for growth" his company wanted to explore.

"The Scotch whisky industry has evolved over the last 16 years and there are now inter-national opportunities for growth that require investment by The Famous Grouse," he said.

"We feel, therefore, it's an appropriate time to stand aside from the high-profile association with the shirt. We are proud to support the national team through what will be a fifth World Cup campaign and wish the squad every success."

Edrington has seen the brand's market share increasing in places such as North and South America, Asia, Spain, Greece and Portugal. It anticipates further growth and wants to concentrate future high-profile sponsorship in these areas.

Sponsorship experts told The Herald last night the SRU may struggle to find such a high-level and loyal shirt sponsor as The Famous Grouse, although there are a few possible candidates.

The Bank of Scotland could be among the leading candidates as they will step down at the end of the season from being sponsors of the Scottish Premier League.

Bank of Scotland Corporate announced earlier this week they would be supporting the World Cup rugby warm-up matches against Ireland and South Africa later in the year and the company may want to increase involvement in rugby.

Glasgow-based brewers Tennants sponsor the Scottish Cup and are heavily involved in the national football team but may emerge as a contender.

A spokesman for Scottish Rugby said they would start active discussions with a number of prospective sponsors but could not divulge details.