Cities like Slovakia's capital Bratislava and Tallinn in Estonia vie for this fast-growing custom with perennial favourites such as Amsterdam and Prague. Research for Morgan Stanley's credit card division indicates friends of a bride or groom will spend an average of #365 for a weekend away celebrating their final hours of singledom.
It was estimated that this year alone more than 3.3 million Britons will spend a total of #532-million on stag or hen events.
Budget airlines to blame
"Five years ago, stag and hen parties were just a few mates having a night out in a pub drinking beer, now they party for two nights at least, and spend a whole weekend together, often abroad," said Caroline Brooks from leading British operator Stagweekends.
Brooks explained that the advent of "low-cost" airlines had played a large part in the explosion of stag and hen weekends to eastern Europe.
With Ryanair offering flights to Riga for as little as #6 (R70), easyJet about to open a route to Tallinn, and SkyEurope to Bratislava, eastern European capitals are becoming as accessible for Britons as previously favoured haunts on home soil such as Glasgow, Newcastle or Brighton.
Dearer cities like Amsterdam and Barcelona are struggling to compete, with punters preferring to take "stags" or grooms to eastern European cities, which are seen as exotic and brimming with good beer and attractive local women.
These cities do not hold their punches as they fight amongst themselves to secure a valuable slice of this tourist market.
Tallinn's stagabroad.com claims the city has "the most beautiful girls in the world", while the Slovakian website boasts of "the reputed beauty of Bratislava girls and women".
All boils down to beer
If the cost of a pint of beer solves the argument, a pint in Prague is almost one-fifth the price of one in the UK.
Brooks agreed with research suggesting that Prague's wealth of strip and lapdancing clubs were a trump card, acknowledging that cities are not chosen for their cultural charm alone.
The tidal wave of party-goers is too much for Britain's Jason Barry, who opened a travel agency in Tallinn but now refuses to deal with stag parties.
"There has been a 30 percent increase in British tourists on the last year," Barry said. "At first the stag week-ends were a bit of fun," he said. "But it has gone beyond that. It's beginning to get irresponsible."
Such drunken shenanigans are not new in Britain, where many establishments, particularly in Scotland, now ban stag parties. This helps explain the migration of stag and hen parties to offshore destinations with a more relaxed attitude to policing.
"Some groups are fine, but others are just too aggressive and behave like animals," said Gleeson. "Big groups from the northeast of England are the worst in terms of their behaviour."