According to a study commissioned by Channel 4 for International Women's Day, men feature in 65% of all broadcast roles during the primetime schedule.
A Communications Research Group led by Dr Guy Cumberbatch studied a sample period of 386 peak time hours on BBC One, BBC Two, ITV1, Channel 4, Five and Sky1 over a seven-week period from July to October last year.
The research team found that just four in every ten women on TV are aged 40 or over, compared to six in every ten men.
Women feature heavily in the soap operas, fulfilling nearly half of all roles, but constitute just four in ten participants in comedy, drama and light entertainment shows.
In factual and news programming, women make up around a third of participants and 69% of the time they are covering "softer" topics, such as health or culture.
The study also found that women are major contributors on factual programming in just 34% of occasions, while they are canvassed for vox pops a third as frequently as men.
"This pilot research measures the gap between what we see in the real world, and what we see on TV, and is the first step in developing a comprehensive measurement of how well TV represents and portrays different groups on screen," said Channel 4's head of diversity Oona King.
"Fundamentally, this is about how we view our world and which groups are hidden from view or significantly under-represented. The gender gap here is quite startling."
Sky News is today marking International Women's Day by featuring a full day's schedule on its rolling news channel entirely produced and presented by women.
"Sky News is constantly pushing the boundaries and we are delighted to be marking this important day in this way with our talented women journalists," said Sky News boss John Ryley.
"Editorially, it will be interesting to see what we cover, but we will ask the question we always do - what is of most relevance to our viewers?"