In September 2006, The Independent described Montgomerie as "emerging as a major player in Tory politics." He was critical of the A-List and argued that the party leader after 2005, David Cameron, was in danger of alienating working-class Tory voters, and pressed Cameron for specific pledges on tax cuts. He supported the introduction of same-sex marriage in England and Wales arguing that it was a way to strengthen the institution more generally. Through ConservativeHome, Montgomerie was used as an expert on internet campaigning by Conservative Central Office.
Montgomerie was a director of the internet television channel 18 Doughty Street which began broadcasting in October 2006 and went off air in November 2007. While at 18 Doughty Street, Montgomerie hosted its 'Campaign HQ' programme, which developed the channel's Internet political advertisements after allowing viewers to vote on a choice of (usually) three different proposals. Previous adverts included attacks on taxes, state funding of political parties, and London Mayor Ken Livingstone. The latest, "A World Without America", with an end scene depicting the Statue of Liberty wearing a burqa, was co-produced by 18 Doughty Street and the website BritainAndAmerica, and had 50,000 views within its first 24 hours of publication.