Kim Howells, the broadcasting minister, has refused to intervene and referred the issue to the Independent Television Commission, which has already made clear it is unsympathetic to a ban.
The Government's decision came in a letter to the Labour backbencher Debra Shipley, who has tabled a Commons motion calling for a ban on ads during "toddler TV".
It has won the backing of 120 MPs - 108 from the Labour Party, seven from the Liberal Democrats, two from Plaid Cymru, one from the Scottish Nationalists, one from the Ulster Unionists and one from the Tories, the former minister Peter Bottomley.
Traditionally, motions that win more than 100 signatures are taken seriously by the Government, but ministers have privately reassured the ad industry they have no intention of bringing in a ban.
The Government's stance has angered Shipley, who accused it of ignoring the research she had admitted to the Department of Culture, Media and Sport on the issue.
"Ministers seem very reluctant to take on the advertising industry and the big media moguls, she said.