If your traditional hand-pulled pint at your local isn't cask-conditioned but actually comes from a keg, that might sound like a technical footnote, but a new tipple from Carlsburg is pumping up opposition from real-ale campaigners CAMRA.

Carlsberg's Marston's Brewing Company (CMBC) launch of a new ale range has triggered a "handpump hijack" campaign from CAMRA as guardians of real ale – with the marketing action of a name synonymous with lager that reaches new parts firmly in its crosshairs.

The keg-delivered and pasteurised ale's launch risks confusing drinkers about cask-conditioned beers, CAMRA says – and it's taking its complaint to Westminster.

An open letter sent by CAMRA to Lord Bishard, who was the chief executive of Shire Hall in the 1980s, calls for National Trading Standards to probe whether the Consumer Protection from Unfair Trading Regulations have been breached by CMBC and seeks an scrutiny of the new beer products, which use a cask handpump to serve beer which is kegged rather than cask-conditioned.

A CAMRA spokesman told Punchline-Gloucester.com: "This is the start of the 'Handpump Hijack' campaign to raise awareness of misleading beer dispense, and make sure that the handpump remains a signifier of cask-conditioned beer."

If successful, CAMRA hopes to stave off a trend which has seen more than 7,000 true hand-pump ales disappear in the last four years.

CMBC makes top-selling ales such as Marston's Pedigree, Hobgoblin and Wainwright - and claims the new keg ale helps mimic the flavour, body, and behaviour of real ale. Significantly though, it has a shelf life of up to 14 days – a significant factor to publicans who often struggle with real ale which can go off within just three to four days.

In the letter, Gillian Hough, National Director and Chair of CAMRA's Real Ale, Cider and Perry Campaigns Committee, said: "CAMRA believes that these practices come under the scope of the Consumer Protection from Unfair Trading Regulations 2008, as the average consumer may choose to buy the product on the basis that they believe it to be cask-conditioned beer, which in this case it is not.

"We believe that this falls foul of the Order's provisions in Section 2 to protect consumers from presentation which is likely to deceive the average consumer or cause the average consumers to take a transactional decision he would not have taken otherwise."

Nik Antona, CAMRA National Chairman added: "Misleading dispense is particularly detrimental to beer drinkers, as hijacking a handpump to serve a keg beer removes a genuine cask product from the bar, reducing choice of different formats for consumers.

"Unfortunately, Carlsberg Marston's Brewing Company have a track record on potentially misleading marketing, having already badged Wainwright as 'A Lake District Original', despite it being brewed over 100 miles away in Wolverhampton.

"We hope that Trading Standards bodies across Great Britain will take swiftly coordinated national action to address misleading beer dispense and safeguard the handpump as an indicator of cask beer."