Harriet Harman has written to national newspaper editors asking them to reveal how many women over the age of 50 they employ.
The letter, sent to all 16 national papers as well as the London Evening Standard, also asks what percentage of women of any age the papers employ, how many women over 50 they have covering politics and how many have senior editorial positions.
It also asks similar questions about their rosters of freelance writers.
Harman said: “I’m writing to national newspaper editors to ask them to be open about the number of older women working in UK newspapers.
“We see the world through news and comment in our newspapers so a balanced team which includes older women is needed to report the world as they see it. Equality is not just important in principle – it is important for the quality of newspaper reporting and comment.”
The deputy Labour leader and shadow culture secretary published a report in May which showed that 18 per cent of broadcasters were women over 50.
She has repeated her call on culture secretary Maria Miller to enforce the “dual discrimination” clause in the 2010 Equality Act, introduced during the last Labour government. The clause allows employees to bring discrimination claims if they have received unfair treatment on two protected characteristics, such as age and gender, where a claim on one ground could not be brought.