Tripadvisor has become the first stand-alone travel brand to reach the milestone of 50 million unique monthly visitors, according to worldwide traffic data from comScore.

Based on comScore data, TripAdvisor has experienced a 22 percent increase in traffic year-over-year from July 2010 to July 2011. TripAdvisor also now features 20 million registered members, up from 15 million in January 2010.

“We are excited that TripAdvisor continues our aggressive growth globally, to help new audiences around the world plan and experience the perfect trip,” said Steve Kaufer, founder and CEO of TripAdvisor.

“We have always believed that user generated content would greatly benefit the travel community and are delighted that this belief has been demonstrated with the site becoming the first in the travel arena to break the 40 million monthly user barrier. The tremendous reception of our site, created by travelers for travelers, underscores the universal appeal of TripAdvisor as the go-to source for travel reviews and planning.”

TripAdvisor has also seen tremendous growth internationally, now available in 14 languages, across 23 countries worldwide.

In 2010 the travel forum launched new websites in eight markets globally, including Turkey, Denmark, Mexico, Poland, Norway, Australia, Singapore and Thailand.

But it is currently being investigated by the Advertising Standards Authority following thousands of claims by hoteliers that its reviews are made up or misleading.