Wales wants fair funding after any DUP-Conservative deal
Any extra money for Northern Ireland under a Conservative-DUP deal at Westminster should also lead to more cash for Wales, say Welsh ministers.
There are suggestions the DUP could demand additional funding for Northern Ireland projects for its support.
Welsh Finance Secretary Mark Drakeford said Wales and Scotland should benefit in a similar way from any cash boost.
"I will have a problem with it if money which is being given to Northern Ireland for purposes that are devolved to Wales and Scotland," he told BBC Radio Wales' Good Evening Wales programme.
A long-running arrangement distributes extra money to Wales, Scotland and Northern Ireland using a mathematical formula when public spending goes up in England.
Mr Drakeford added: "As John Major has said, if this turns out simply to be cash for votes, then that is a very, very undignified position for the UK government to have put itself in.
"If there is money for purposes that only exist in Northern Ireland, that's one thing; but if Northern Ireland were to benefit for purposes we ourselves have to discharge here in Wales, we will expect to see a similar sum of money calibrated to our size and circumstances to come to Wales.
"It cannot possibly be that there is a separate flow of money to Northern Ireland only for responsibilities that are at the same time discharged in Scotland and in Wales."
The devolved government in Belfast is currently suspended.