Lord Bragg, who is also the controller of LWT's arts department, criticised the amount of "laddish TV that has turned into loutish TV" which keeps the discussion of ideas out of television schedules.
His attack follows weeks of complaints by television figures about declining standards. Last week, John Humphrys, the former BBC television news reader who now presents Radio 4's Today programme, declared that news and current affairs programmes were losing their bite.
Before him, Noel Edmonds, the man who brought the country Noel's House Party and Mr Blobby, complained that the BBC's standards were falling because of spending cuts.
Lord Bragg, whose new South Bank series has programmes on the actress Joan Collins, the singer Cher and the Lion King musical, denied that the show could be accused of following a similar middle-brow trend as the rest of television. He said: "I am not embarrassed by doing programmes on popular culture. The first show we did 23 years ago was on Paul McCartney. Joan Collins is an iconic figure and we can do Dolly Parton just as interestingly as a programme on Tony Harrison.
"I am talking about a lack of ideas on television. We have a better-educated population than ever before and they have to go to newspapers or Radio 4 to get the discussion of ideas. I love television and I think it should be doing it all, and putting forward programmes about thinking. There is an audience for ideas which would surprise some people. When we started In Our Time on Radio 4 I inherited an audience of 600,000 and now it's at 1.5 million. People are going out and packing into lectures, the book festivals are crowded, but people have this idea that television cannot be a forum for the ideas that are being thrashed around.
"British television is still led by some extremely able people, and yet at times they can seem like thoroughbreds happy to pull milk carts. Am I alone in believing that here as elsewhere Trash TV is welcomed because there are those in the opinion-forming seats who still feel that all TV is trash and all proofs to that absurd theory are welcome?"
Lord Bragg was unveiling LWT's arts and features programmes for the next year, which include a look at the Ten Commandments, a history of the British hit single, and a premiere of Thomas Ades's opera Powder Her Face.