Wales is owed 'reparations' from the UK Government for a 'century of neglect' according to Plaid Cymru's leader, Adam Price.
Mr Price has called for a 'Welsh Reconstruction Fund' to be set up to compensate for what he described as Wales being "ground down into crippling poverty" by "British rule".
Plaid Cymru say it is not charity but "justice".
In October last year, the UK Government said it was allocating "more than half a billion pounds" of additional funding for the Welsh Government, including £120 million for the North Wales Growth Deal.
Through the Barnett Formula for devolved government budgets, spending per head in Northern Ireland last year was highest at £11,190 per head, followed by Scotland at £10,881 per head and Wales at £10,307 per head.
England was lowest at £9,080 per head.