London Clubs International runs upmarket casinos in London and across the UK, and is part of Harrah's Entertainment Group - the world's largest casino operator.
The company's executive director Roy Ramm said: 'We wanted to find an agency that would help develop our relationships with existing MPs and officials, but also extend our reach on the Conservative benches. In particular, we wanted a company immersed in the politics and policies of the Conservative Party.'
DJH was set up in 2001 by Richard Jukes, a former aide to Tory MP David Mellor. Current clients include the British Casino Association.
Jukes said of the brief: 'Our challenge is to change the perception of casinos among the new intake of MPs, who will most probably have been influenced by sustained editorial opposition to gambling in large sections of the press.'
Tory leader David Cameron has told close colleagues that he believes he is on course to win 140 new Tory MPs after the next election, according to reports. The ConservativeHome website analysed candidates in the 100 most winnable seats earlier this year.
The Times reported that the results suggested Cameron would head a party dominated by MPs 'more socially conservative and less concerned with the environment than their leader'.