A watchdog has said it was "concerned and disappointed" after a council refused to repay a foster care-leaver whose savings were not monitored.
The public services ombudsman for Wales asked Bridgend council to pay £3,310 to Rob Johnson, 18, after he said some of his money paid for trips, but the council said it raised national issues.
Nick Bennett warned of further action if the payment was not made.
The council said it took its role as corporate parents extremely seriously.
Mr Johnson, who was two when he was fostered, said he felt "let down" by the council.
"It would make me feel a lot much more relaxed, I would have something to fall back on if anything went wrong. It would make my life better," he said.
The ombudsman's report noted the council's monitoring of the savings was "intermittent and inadequate" and amounted to maladministration.
There was no criticism of the foster carers in his report, which only dealt with the council's actions.
The council failed to keep adequate records or retain his saving books at the end of his placement, meaning it was unclear why the amounts were as low as they were.
Mr Bennett said: "The only way in which we can see justice done and to really put things right for this young man, who has just come out of care, is to make sure that he receives this payment."
The ombudsman will meet Bridgend council officials on Wednesday.
Mr Bennett said he hoped he would be able to persuade them it would be "a very disappointing message to the people of Bridgend and further afield if they cannot see that they have a responsibility to put this wrong right".
If the council does not budge, Mr Bennett warned he would issue a further special report about the case - the cost of which would have to be borne by the authority.
He added: "It might well be that there is a resistance to implementing this specific recommendation because it sets some kind of precedent.
"My interest is not in that; my interest now is in ensuring that justice is done for the individual that came to see us."
Bridgend council said it would comply with all of the ombudsman's recommendations except making the payment.
A spokesman said: "The issue here is that councils are powerless to make carers save on behalf of looked-after children as there is no legal requirement or national policy in place requiring them to do so.
"As we cannot enforce this, we are limited to asking foster carers to either save themselves or encourage the children to start saving.
"As the ombudsman has recognised that this case raises issues at a national level, it is inappropriate to seek to deal with it on a local level."
Children's Commissioner Sally Holland said the case highlighted a "crack in the system," set against a background of hundreds of children leaving care and facing struggles to make ends meet.
She added: "The Welsh Government and the Welsh Local Government Association need to be looking together at the consistency of how rights to savings and to pocket money are being applied right across Wales and to make sure that that's consistent and fair right across the board for all looked after children."