Equalities minister Harriet Harman accused the BBC of "wasting a lot of talent" and upsetting viewers by not valuing older female newsreaders.
Ms Harman, who is also Labour's deputy leader, said that female BBC news presenters had to be 10 years younger than their male counterparts.
She told the BBC's World This Weekend: "It's essentially an old-fashioned attitude that thinks you can't value the experience and wisdom of an older woman."
Ms Harman's intervention comes after the BBC pledged to appoint a female newsreader over 50 in a bid to defuse an ageism row.
She said: "I think that the broadcast media finds it possible to value the older man but I don't think they find it possible to value the older woman.
"A former senior BBC executive said to me: 'the thing is, the way we saw it was that as male presenters got older they become an authority and as female presenters got older they became a problem'.
"To be a BBC news presenter as a woman you have to be 10 years younger than the men.
"They should be very careful about it and I think they should be anxious and worried about it... and I think they're wasting a lot of talent and annoying a lot of viewers."
In 2007 the corporation came under fire for dropping Moira Stuart, then aged 58, from her Sunday AM slot after more than 30 years as a BBC newsreader.
The axing of Arlene Phillips, 66, who was replaced as a Strictly Come Dancing judge by 30-year-old Alesha Dixon, sparked fresh accusations of ageism last year.