The reluctance of ministers to halt the commercials was challenged at a conference at Westminster on Wednesday to launch a new backbench bill.
The bill proposes a ban on junk-food commercials during children's programmes and asks that the existing code is replaced by a statutory one. It is due to have its second reading on 28 October.
The strong support for the Children's Food Bill will put pressure on ministers to keep open the option of a ban even though they admit privately they want to stick with a voluntary approach. In turn, the MPs' demand could force the food and drinks industry to offer further curbs on ads as it draws up a new code.
Labour MP Mary Creagh, who is introducing the Bill, has won the backing of 194 other MPs for a Commons motion backing its principles. At Wednesday's conference, she was promised the support of 150 campaign groups including four big trade unions.
In a briefing note to MPs, Creagh said the Government had identified the problem but it proposed "yet more consultation and voluntary codes of practice".
She warned that, if current trends continue, another 440,000 children may be obese by 2007, when ministers will finally decide on a ban.
- Comment, p48.