The trip, which kicked off Wednesday, has sparked heavy criticism among parliament officials and journalists.
It is not only being held while the House is in session, but the programme was also more oriented towards tourism activities than study. It includes attendances at English Premier League matches in London on Saturday and Sunday.
One member of the trip, Virot Ali, is listed as attending in the role of "Bangkok Post columnist". Mr Virot, a political science lecturer at Thammasat University, has no affiliation with this paper.
Mr Virot, an occasional commentator for Voice TV, did not know why he was listed as a Post columnist.
"The invitation came from parliament at the last minute, and stated that it was an academic study tour to observe water management systems," Mr Virot told the Bangkok Post.
"I certainly do not know how [the organisers] listed me as attending on behalf of the newspaper, and will ask them to make a correction."
An invitation to attend the three-country trip with the House speaker was made to Post columnist Voranai Vanijaka in late August, but the newspaper declined the invitation.
Chabaporn Aungkasukho, a representative of Skylight Elegance which organised the trip, said the listing was a printing error and it has been corrected.
The itinerary for the nine-day trip to England, France and Belgium includes visits to the Economist and BBC Broadcasting House in London, the French parliament and Musee du Louvre in Paris and the European parliament in Brussels.
A source, who declined to be named, said the trip's 7 million baht cost (180,000 baht a head) comes from the 2012 fiscal year budget ending on Sept 30.
Mr Somsak assigned first deputy House Speaker Charoen Chankomol as acting House president and Senate Speaker Nikom Wairatpanich as acting parliament president during his absence.