Scotland's First Minister Alex Salmond has dismissed David Cameron's speech on the Scottish referendum as "flimsy" and repeated his challenge for the Prime Minister to agree to a head-to-head debate on the issue.
His comments come as the Prime Minister made his highest-profile intervention in the debate on Scottish independence so far by calling on England, Wales and Northern Ireland to persuade Scotland to stay in the union.
The SNP leader said: "This speech was a threadbare defence of the case for Westminster Tories retaining their undemocratic control over Scotland, which betrays the utter weakness of the Prime Minister's case.
"David Cameron said he will 'fight with all he has' against Scotland's independence - but that doesn't extend to having a head-to-head debate on the subject."
Speaking at London's Olympic Park, Mr Cameron called on the people of England, Wales and Northern Ireland to send a message to Scotland as it prepares to vote on September 18: "We want you to stay."
Independence would be bad for Scotland but would also leave the United Kingdom "deeply diminished" and would "rip the rug from under our own reputation" in the world, Mr Cameron said.
The Prime Minister received support for his cause from Wales: the Welsh First Minister Carwyn Jones urged Scots to vote no to independence.
He said his message to the Scottish people was: "As fellow Celts, stick with us in the union that's benefited us so much over the years."