Holyrood’s Social Security Committee heard how children desperate for food go through parcels as soon as they are handed over to see if there is something they can eat straight away.
One man had not eaten any food for four days before coming for an emergency package, with the committee told he had been surviving on water alone over that period.
One Edinburgh agency has seen a 50 per cent increase in referrals this year.
Laura Ferguson, of the Trussell Trust charity, which has 53 food banks across Scotland, said demand increased by up to 80 per cent at some of its centres after the roll-out of Universal Credit welfare reforms.
She spoke about the “invaluable work” food banks do, telling MSPs: “There is no doubt that food banks save lives.
“They are there, they provide emotional support, they provide wraparound services to help people in their situation.”
But she added: “We can not forever rely on food banks to pick up the pieces of a failed welfare state.
“We cannot further institutionalise food banks, they do do amazing work but they just can not be here forever.”
The Trussell Trust handed out more than 170,000 food parcels to those in need in Scotland last year - a rise of 17 per cent on the previous year.
Joyce Leggate, the chairwoman of Kirkcaldy Foodbank, told MSPs about families coming to get food during the holidays.
She said: “Over the school holidays, the October holidays in particular, we had quite an increase in the number of children that are right in the parcel, in the food bank, opening stuff up to see if what they could eat on the way home, whether it is a packet of biscuits or anything.
“If we have any bread to give out it is getting eaten before they go home, which really is quite shocking to see that level of hunger in children.”
Meanwhile, Aziz Zeria, the treasurer of Crookston Community Group, said: “We had a young child who had been eating tomato sauce at school and then coming to us for food, then receiving a note to say ‘thank you for giving my mum food so we can eat some food’.”
In another case, his organisation helped a divorced father-of-two who “hadn’t eaten for days, surviving on water for four days, he had no gas and electricity”.
Mr Zeria said: “He received three parcels from us over a period of time, plus some top-ups so he could have utilities in his house, this allowed him to see his children for the first time in many weeks.”
Stever Wright, of Edinburgh City Mission, said the nine food banks it has in the city have had a 50 per cent increase in referrals this year.
He told MSPs a number of people it helped were in jobs but had experienced problems with in-work benefits or were simply struggling to cope with rising food costs.
He said: “It’s not just a spike this year, it is a problem that has been building and now it has reached crisis point.
“Last year, we gave away 100 tonnes of food, this year we’re going to be substantially over that.”
Mark Frankland, the manager of the First Base Agency in Dumfries, said those in work often waited for months before asking for help.
He told the committee: “The people we see who are in work, when you have a conversation with them, they really should have come about six to eight months earlier.
“And in that six to eight months the credit cards have got maxed out, mum and dad can’t lend them any more money, and that is almost entirely down to stigma.”
He added: “I get the impression there is a big cliff edge we might be getting to where people who are in work, they leave it until the absolute last resort before going to a food bank.
“You do get the feeling there is a lot of people who are coming to that cliff edge and when they do come out, it could take quite a lot of dealing with.”
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