The beer of choice under the pergola and around the pool is increasingly Boag's, a beer made in Tasmania, owned by the Japanese and sold by the truckload in Victoria.

Goldman Sachs JBWere analyst Ian Abbott believes Boag's, part of Lion Nathan's portfolio, is on the cusp of a fresh wave of popularity in VB's home territory.

He said that if the penetration continued, it could sink Foster's national market share and cost the beer and wine company $100 million in revenue and $40 million in pre-tax earnings. Mr Abbott said that after years of failing to crack the fiercely loyal Victorian market, Lion Nathan now had a brand that resonated with Victorians.

Placing a ''sell'' on Foster's stock, Mr Abbott said the timing was perfect for Lion Nathan as social trends showed consumers were increasingly willing to try new brands.

''If … Lion Nathan is successful in gaining traction in Victoria - current growth for Boag's is at least 30 per cent - then this would suggest there is a risk of a modest downwards trajectory to Foster's overall market share over the next few years,'' he said. Foster's market share in Victoria has traditionally been 85 to 95 per cent.

''If Lion Nathan were to direct most of its Boag's mainland Australia capacity - say 60 million litres - to the Victorian market, then in time we believe Boag's alone could capture 15 per cent of the Victorian beer market and Lion Nathan's aggregate position in Victoria would improve to 20-25 per cent market share.

''If Foster's share of the Victorian beer market were to fall from its current 85 per cent to 75 per cent, then, on our analysis, its share of the overall Australian beer market would fall from 50 per cent currently to around 48 per cent - which is the equivalent of a drag of around $100 million in revenue, or around $40 million in EBIT [earnings before interest and tax].''

A spokesman for Foster's said Victorians remained strong supporters, with its CUB beer brands taking nine of the top 10 positions in the state.