The UK government should ask for the assembly's permission before imposing charges to pay for services which are devolved in Wales, a Labour AM says.
From April, a new way of providing apprenticeships in England, funded through a UK levy, will begin.
But Welsh ministers responsible for apprenticeships here said they will not get new money from the charge.
Jeremy Miles said it was a "mess". The UK government said it was an assembly matter.
The UK government is introducing a UK-wide levy on larger employers to raise funds for apprenticeships, saying that Wales would get about £130m a year from the charge.
All employers with a wage bill of more than £3m a year will pay 0.5% on it.
But the Welsh Government said it had lost out on funding elsewhere from Westminster despite the extra cash.
Welsh ministers have their own scheme - for which they announced an extra £15.5m in February - although firms have been urging Welsh ministers to ring-fence the levy cash.
"The UK-wide levy is a bit of a mess of a policy," said Mr Miles, a backbencher who serves the area of Neath.
"What we should have is a situation where, if the UK government wants to raise a levy to pay for the apprenticeship policy that applies in England, they should do that.
"But that shouldn't capture companies or operations of companies based in Wales where there's a very different apprenticeship policy."
He said the levy had "driven a coach and horses" through democratic devolution.
"Imagine if you have a situation where the UK government, or the English government, decided to put a penny on national insurance to pay for a particular policy in the English NHS, or put some money on national insurance to pay for social care for example," he said.
"You can then imagine how difficult that would be, which represents a much bigger part of the Welsh Assembly's work and the Welsh Government's operation and budgets".
In future, he said the Welsh Assembly should have the power to consent or withhold consent to any proposed UK-wide charge which would affect Wales.
"Brexit is going to mean that we are once again around the table with the UK government arguing over funding formulae and powers - this should be on the table," he added.
A spokesman for the UK Department for Education declined to provide a statement, but said it was an assembly policy matter.