The channel is targeting a key advertising audience of ABC1 35 to 55-year-olds with a range of programmes that match the feel of the parent channel.
C4 chief executive Andy Duncan, speaking at the channel's official launch at the Edinburgh International Television Festival last week, said More 4 would help boost Channel 4's presence in multichannel homes, which was currently around 8% compared with 13% in non-digital homes.
Channel 4 director of network marketing Polly Cochrane told Media Week that a campaign including TV, press and outdoor, valued at £1m to £5m, would kick-off in mid-September.
"We're spending millions but, as ever, the off-air component will be dwarfed by the Channel 4 component," Cochrane said. "The launch is of a similar scale to the launch of E4. We want it to feel like a big event. You only get the opportunity to launch once."
OMD will do the media buying and DDB the creative work, while Michaelides & Bednash will handle media strategy and Spin the channel identity.
More 4 will initially broadcast from 4pm to 4am and will be available on Freeview, Sky and cable.
Kevin Lygo, C4's director of programming, said he was focused on quality rather than ratings. More than two-thirds of the £20m programming budget is dedicated to original British content, including a feature length comedy on the David Blunkett affair, called A Very Social Secretary.
US imports include The West Wing, comedy Curb Your Enthusiasm and The Daily Show, an irreverent talk show hosted by Jon Stewart.