The decision to dump the Melbourne, Sydney and Brisbane editions of the current affairs program, effective immediately, was announced on Monday morning.
Local editions of Today Tonight will still be produced in Adelaide and Perth where it has a very strong following.
Seven’s move to an hour-long news service follows Nine’s lead, which on January 6 started airing a national one-hour bulletin from 6pm.
A Seven spokeswoman told AAP it was not a knee-jerk reaction.
“We have been working on this for 13 months and the time is now right for us to go ahead with it,” she said.
There will be no retrenchments and Today Tonight staff in Melbourne, Sydney and Brisbane will join the news teams, she said.