Carwyn Jones disputes Plaid Cymru's £1.2bn underfunding claim
The first minister said he does not recognise a Plaid Cymru claim Wales needs an extra £1.2bn funding a year.
Plaid leader Leanne Wood accused Carwyn Jones of running a Labour party branch office and not standing up for Wales.
Mr Jones focused on an estimated shortfall of £300m, identified by economist Gerry Holtham five years ago.
At its conference in Llangollen last month, Plaid Cymru said £1.2bn more was needed to give Wales "parity of financial resources" with Scotland.
Former Plaid leader Lord Wigley told the conference that if Wales "got as much pro-rata as Scotland gets in comparison to England, then our national assembly would be getting £1.2bn more each year".
He accused successive UK governments of being responsible for the "deliberate" and "chronic underfunding" of Welsh public services.
But during First Minister's Questions on Tuesday, Mr Jones said: " I do not know where that £1.2bn comes from.
"What we do know is that there is all party agreement of the Holtham Commission that identified £300m.
"I expect my party to address that shortfall."
Earlier, Ms Wood said Wales deserved "at least parity of resources with other parts of the UK".
"Plaid Cymru has highlighted the £1.2bn annual price tag of the inequality of funding between Wales and Scotland."
"Plaid Cymru reiterates the need for us to be treated equally - not special treatment - fair treatment," she added.