UK government support for the Scunthorpe steel works cannot be at the expense of Welsh steel communities, Eluned Morgan has said.
The Labour first minister said she "understood" why Welsh communities were "frustrated" after Westminster stepped in to take control of Scunthorpe steelworks.
Morgan called for her party colleagues in Westminster to provide a "significant share" of a £2.5bn steel fund in Wales, and warned against spending the funds on keeping the British Steel plant going.
Plaid Cymru have accused the UK government of double standards over the Port Talbot plant, which has seen its blast furnaces close. Business Secretary Jonathan Reynolds has denied favouritism towards Scunthorpe.
The Welsh Conservatives said many were unhappy with the different approaches.
Morgan defended the decision by the UK government, says the two situations were not comparable and it would have been "unrealistic" for ministers to take control of Port Talbot.
But she said she would be making a speech next week on how she plans to work with the UK government in future.