New research shows fresh own-label milk sold in four-pint bottles is cheaper than the average price of larger packs and multipacks of bottled water

Milk is now cheaper to buy than bottled water thanks to a fierce supermarket price war.

Supermarket price wars have pushed the price of four-pinter milk below that of some bottled waters.

New research shows how, based on price per litre across the big four supermarkets, fresh own-label milk sold in four-pint bottles has become cheaper than the average price of larger packs and multipacks of bottled water.

When bought in a four-pint bottle, the price per litre of milk has dipped to 43p, compared to 44p for bottled still water.

However, the price war has angered farmers who complain that supermarkets are forcing down their income.

Four-pint bottles of milk have become a key weapon in the ongoing grocery price war and suppliers fear another raft of retailer cuts after Asda this week slashed the price of four pints of own-label milk from £1 to 89p.

At the start of last year, there was a gap of about 2p or 3p between a litre of water and a litre of milk sold in four-pinters, with the big four selling the bottles for £1.39, according to research by The Grocer magazine.

While price cuts have been mainly focussed on four-pinters - leading to a drop in price of nearly nine per cent - the price of many other formats has also fallen. Excluding four-pinters, the average price of a litre of own-label fresh milk at the big four has dropped from 83p to 78p - a decline of six per cent.

The Grocer's research also reveals how cheap milk is compared with other popular drinks.

On average, a litre of one of the top five lager brands is almost five times more expensive than four-pinter milk.

Lager - also a key weapon in the price war - hasn't been immune to price erosion however, falling 2.2 per cent from £2.10 a litre to £2.05 a litre between January 2013 and this month.

World Cup activity had pushed the price to £2.01 in June, while it slumped to £1.95 in the run-up to Christmas.

Orange juice - which costs more than three times the price of milk - has fallen in price by nearly four per cent this year.

The price of cola has also risen this month after plunging to 85p a litre ahead of Christmas. At 99p a litre, it remains more than twice the price of a litre of the white stuff.