First published in 1855, the title has been a mainstay on Merseyside for well over 150 years. However Trinity said that people's buying habits were changing, forcing it to adjust the way news was consumed in the area.
Post Editor Mark Thomas said: "We’ve just completed research which proves yet again how much people like and want our current content mix. However, we appreciate that the world is changing and people’s buying habits and news consumption requirements are very different.
"There is clear evidence that a bumper Post once a week, full of high-quality news, views and analysis, will be better for readers and a more appealing vehicle for advertisers.
"We realise there will be many Post followers who will still want a daily update on the news. We will make sure that they get that through our website, which will update all news with our usual special emphasis on business, sport, the arts, and politics."
The move will result in the loss of six editorial roles, although jobs are unaffected at the company's Oldham print facility.
At this stage it is unclear what the run length of the new title, currently expected to be the Liverpool Post, will be. The Liverpool Daily Post has an average circulation of around 8,000 copies per day.
Trinity has also announced that the free Liverpool weekly titles The Bootle Times, Merseymart and Star will be merged into two new community newspapers, The Star and The Merseymart.
Both titles will be carried to market within the Tuesday edition of the Liverpool Echo.