One in every 10, two-pint semi-skimmed units are bought in bags – some 120,000 a week – and more than 4,000 RPC-manufactured Jugit containers are sold every week.

From today (11 August), whole milk will be available in the format and skimmed and 1%-fat versions will launch next June.

Sainsbury's expects that increasing the number of varieties will double the amount of bags sold.

Positive consumer response
Sainsbury's senior dairy buyer Emma Metcalfe King said the supermarket had been blown away by the response.

"Rather than being wary of the new packaging, customers have lapped up the bags. Sales are so good we are now investing in a new processing plant to keep up with demand," said Metcalfe King.

£2.2m investment in processing
Sainsbury's and supplier Dairy Crest have invested more than £2.2m in a new processing plant in Gloucestershire creating 20 jobs.

The move to milk in low-density polyethylene bags forms part of Sainsbury's move to meet its target to reduce packaging by a third by 2015.

The bag uses 75% less material than the equivalent two-pint bottle, and Sainsbury's said the switch to bags would save 1,400,000kg of plastic a year.