A European Parliament spokesperson said it was "very, very unlikely" that members would vote to force Britain to sell milk in litres rather than traditional pints.
The European Parliament will hold a second vote Thursday on amended proposals from the European Commission to deregulate packaging sizes for consumer products.
MEPs have already voted once to allow imperial measurements to continue alongside metric ones as part of several amendments to the proposal. And, the spokesperson said they would probably do so again because Thursday's ballot only allowed members to vote for all or none of the amendments.
His comments followed the launch of a public campaign to save the British pint by the British Retail Consortium.
Jim Begg, director general of dairy industry association Dairy UK, said the dairy industry had also been lobbying to keep the pint.
Dairy UK's policy director, Peter Dawson, said a switch to metric sizes might well cost processors and packaging firms millions of pounds to change products, containers and equipment, as well as confuse consumers.
The European Commission put forward its proposal to allow industries, including food and drink, to produce and sell goods in whatever size they chose. This, it said, would increase market competition and improve consumer choice.
The Commission proposed to retain set sizing for only a few goods, including spirits, wine, soluble coffee and white sugar.
MEPs voted in December to add drinking milk, butter, ground or unground roasted coffee, dried pasta, rice and brown sugar to this list. Yet, they also backed an amendment that would allow imperial measurements to continue.
The European Parliament's Committee on Internal Market and Consumer Protection said: "Products such as these, as staples of the average consumer's diet, should only be sold in a restricted number of sizes.
"Otherwise, consumers risk being misled into buying a cheaper bottle of milk or a cheaper stick of butter without realising that it contains a smaller volume."
At the second reading this week, widely expected to pass, a further amendment will be included. This would give member states the option of retaining set pack sizes for another three products: tea, pre-packed bread and all spreadable fats.
If MEPs back the amended proposal again, it will return to the Council of Ministers for approval.
Yet, if the Council does not agree, then both it and the Parliament will have to sit down and thrash out a compromise; something that could lead to certain amendments being dropped.
The Parliament spokesperson said the Council was more in favour of deregulation than most MEPs.