Channel 5 beat Channel 4 in the overall overnight ratings last week for the first time in the broadcaster's history.
Boosted by the latest series of Big Brother and its coverage of England's Ashes success, Channel 5 picked up a 5.0% viewing share, according to live overnight data.
Channel 4's share for the week by the same measure was 4.9%.
This is the first time on record that Channel 5 has beaten Channel 4 in viewing share across a weekly period. Channel 5 is up 9% year-on-year from the same week in 2012.
Meanwhile, Channel 4 was down 22% year-on-year.
Ben Frow, Channel 5's director of programmes, said: "We've been working really hard to give viewers what they want and we are really glad that they have been enjoying our progress."
Channel 4's poor ratings have put the broadcaster in the spotlight over recent weeks, and channel boss Jay Hunt's position has come under extra scrutiny as a result.
