Devolved leaders oppose UK spending cuts
The first ministers of Scotland, Wales and Northern Ireland have issued a joint declaration attacking the UK government's spending plans.
The leaders of the three devolved administrations said the coalition's cuts are "too fast and too deep" and may put the economic recovery at risk.
Alex Salmond, Carwyn Jones and Peter Robinson want cuts phased in over a longer period.
The prime minister said that approach would worsen the debt problems.
In his speech to the Tory conference on Wednesday, David Cameron said only Labour opposed to the UK government's deficit reduction plans.
But the rainbow alliance of parties which run the three devolved administrations, which includes the SNP and DUP, says frontloading spending cuts over the next two years is "entirely the wrong approach for the economy" and risks stalling any recovery.
They say: "The devolved administrations believe that the proposed approach to public spending reductions by the UK government runs the risk of delivering significant economic and social harm and urge the UK government to reconsider its proposals."
The statement is signed by Peter Robinson and Martin McGuinness in Northern Ireland, along with the SNP's Alex Salmond and Carwyn Jones of Labour, whose party is in coalition with Plaid Cymru in the Welsh assembly.
The deputy first ministers and finance ministers in all three countries also gave their support to the joint declaration.
Mr Salmond described the move as an "unprecedented display of unity", adding: "It is essential that we do all we can to ensure and support a strong economic recovery.
"However, the scale of the spending cuts proposed by the UK government risk jeopardising this work and causing significant harm to the economy at this critical period."
Mr Jones said: "We have taken this unprecedented step because we believe the scale and speed of cuts we have been led to expect will have devastating consequences for the most vulnerable people in our devolved nations and the impact will be felt for generations to come.
"Our joint declaration shows the strength of feeling within the devolved governments, which represent nearly 10 million people, or one sixth of the UK's population."
In his speech, Mr Cameron accused Labour of having "mortgaged Britain to the hilt", and said of the planned cuts: "I wish there was an easier way but I tell you: There is no other responsible way."
Responding to the declaration, a UK government source, said: "The independent Office for Budget responsibility predicts sustainable growth as a result of our plans, and, just last night, the president of the World Bank praised them as courageous, important and wise."
The scale of the cuts will become clear when the UK government announces details of its spending review, on 20 October.