Philip Davies said he was sorry for the error, telling MPs that he was not influenced in any way after accepting the freebie from Ladbrokes in March 2011.
The MP for Shipley had "properly and accurately" detailed the trip in the register of interests. But under parliamentary rules, MPs must tell colleagues if they have ever accepted any related interests before speaking in a debate or tabling questions.
Mr Davies said that he had subsequently submitted three parliamentary questions on problem gambling, held an adjournment debate on problem gambling, and been a member of the Commons Culture, Media and Sport select committee when it held an investigation into the Gambling Act 2005. The chief executive of Ladbrokes gave evidence to the committee during the investigation.
His apology follows a complaint to the parliamentary commissioner for standards but it was dismissed.
The MP said he also offered his resignation to the select committee if any member felt he had acted improperly but they had turned it down. He also insisted his trip had not influenced his input to the committee's report in any way.
Mr Davies added:
Speaker John Bercow thanked Mr Davies for his statement.