A ban on advertising junk food before 9pm could wipe out the production of children's programmes, says a report.
Almost a third of children in the UK are now overweight
Commercial channels could lose £114m from such a ban, which is over double the amount they spend on children's TV, says producers' trade body Pact.
Media watchdog Ofcom is looking at ways to curb food adverts aimed at children, although it says a pre-watershed ban would be "disproportionate".
Pact has called for a fund to ensure the future of children's television.
The Children's Rights Fund would invest in 10 new programmes a year, using £50m of government money as a recoupable investment over eight years.
Pact chief exectutive John McVay said children's programmes "must not be destroyed as a result, however unintentional, of proposals for advertising restrictions".
Earlier this year, Ofcom proposed tighter restrictions on the timing and content of junk food commercials as part of a consultation.
One option was to ban the ads in commercial breaks in programmes for pre-school children.
Another was to ban or restrict them in programmes for the under-10s.
It stopped short of proposing a total pre-watershed ban, arguing it would cost broadcasters up to £240m every year.
The government's food watchdog, the Food Standards Agency, disagreed, and said such a ban would extend protection to older age groups.
In May, it emerged the National Heart Forum was preparing an application for a judicial review over the consultation.
The heart charity said it was unlawful and unfair to exclude the possibility of a pre-watershed ban.
However, Ofcom dismissed the idea again in June when it updated its consultation document, although it invited further comments on the issue.
The deadline for responses to the consultation was 30 June. A decision has yet to be reached.