The "political warfare" between a leading foodbank charity and the Government is a "disservice to the hungry", MPs have warned.
Too many children have hunger as their "most constant companion" with one in five pupils at some schools arriving ravenous each day, according to the cross-party group.
A rising number of children are starting their first and final years of primary school underweight while the number of infants and pregnant mothers with anaemia is going up, the Britain's not-so-hidden hunger report said.
Malnourishment in hospital admissions is also on the up, the All-Party Parliamentary Group (APPG) on Hunger added.
Chairman Frank Field said two "very troubling forces" - a breakdown in parenting and a rise in the number of families on low incomes - were behind the "tragedy".
But he questioned whether the issue was failing to get traction with voters because "they no longer believe the data" that is published.
He warned the "political scrap" between foodbank charity the Trussell Trust and ministers was turning attention away from the issue.
Former Work and Pensions Secretary Iain Duncan Smith was among those who clashed with the charity when he accused it of "scaremongering".
Mr Field said: "At a grassroots level the Trust has been successful in enabling individuals, mainly church members, to respond to the quiet pleas from the hungry. The Group has always saluted this group of workers, whether they have been in Trussell Trust or independent food banks.
"But the political warfare that has broken out between the Trussell Trust and the Government is a disservice to the hungry. Voters' attention is concentrated on this political scrap, rather than on the basis of the argument which is over the numbers of hungry.
"It is crucial that the Trussell Trust is more careful in the presentation of the numbers of hungry. The Trust does the most valiant work, but it needs to always register the fact that it probably presents data for less than half of all the organisations helping to feed the hungry. And when it does present the facts it is crucial that the Trust recognises and spells out clearly the complications and intricacies that lay behind them."
The APPG has called for help from the United Kingdom Statistics Authority to help flesh out data about the true scale of hunger across Britain.
Its report looked at 19 schools in Birkenhead and 13 in South Shields, with some staff reporting increased hunger in pupils on Mondays and after school holidays.
Mr Field told how "one little mite in Birkenhead" at a fun day, said "I don't mind missing the activities, but please can I come in and eat? I've had nothing today and I'm starving".
The average household required 25% of its income to cover the costs of food, fuel and housing at the end of 2014, an increase of 5% since 2003, the report stated.
Mr Field said: "Something very troubling is happening and there are at least two forces operating. One is the breakdown in parenting, and the second is an increase in the numbers on a low income. It's a tragedy if one of these strikes a child, but it's an unbounded horror if a child is hit by both. How can the world's fifth richest nation not know the extent of physical damage caused to its own children by a lack of food?
"Too many people in Britain are hungry. How many? We do not know. A very large part of this group of hungry people are children. Again we have only impressions which suggest that too many children have hunger as their most constant companion."