Former British Prime Minister Gordon Brown
Brown has called for Cameron to debate with SalmondReuters

Gordon Brown has weighed back into the Scottish independence debate calling for David Cameron to debate with Alex Salmond and claiming the "Better Together" campaign was fighting on the wrong message.

Speaking to political journalists in Westminster, the former prime minister became the most senior Westminster politician calling for a head-to-head debate between the prime minister and Scotland's first minister.

He said he believed it would be "a good idea for David Cameron to debate with Alex Salmond", something the prime minister has ruled out amid concerns such a clash would only boost the independence campaign.

Brown appears not to have the same concern, but added: "The prime minister has got to be involved (in the campaign) but he has to put the debate properly."

And in what amounted to strong a criticism of the government's role in Better Together campaign led by Labour's Alistair Darling, he said it had been framed in the wrong way with it appearing to be about English politicians telling the Scots what they could not have if they separated.

"Do not let it become English politicians against Scotland, that will play into the nationalists' hands," he said.

His intervention, coming as the rival campaigns marked 100 days to the referendum, was seen as another attempt to add some weight and a more positive message to the "no" campaign, which has recently found itself on the back foot.

"If Britain does not wake up, there will be home rule for Scotland," he said insisting he wanted the "no" campaign to offer a patriotic vision based on the acceptance that the UK was no longer a unitary state.

Scotland already had substantial independence and that would increase, he said. But there was a difference between strong countries with their own identities working together and separation in a globalised world where states were increasingly seeking to forge partnerships.

The campaign should be between two visions, one which was patriotic, with Scotland having its own parliament, strong sense of nationhood, institutions, and more powers and the nationalist vision which was about "breaking every link" with the UK.

That would mean severing the link on everything from defence and healthcare to pensions and the BBC, he said.

Brown insisted he was not attempting a comeback into "front line politics" but was getting involved in the campaign because of the effect separation would have on his children and grandchildren.

But it is thought the Better Together campaign fear they are losing ground to the SNP and a heavyweight figure like Brown, who retains huge respect and influence in the country, is needed to present a more positive anti-independence message.