DAVID Cameron will “stumble” into a fresh referendum on Scottish independence, Jim Murphy has predicted. The former Scottish Labour leader accused the Prime Minister of being so “lame-assly dumb” on the issue that he will give the SNP an “excuse” for another popular vote.

Nicola Sturgeon’s party would hold a poll whenever it “can get away with it”, he added.

His comments were made during a question and answer session at the Policy Exchange think tank in London where Murphy, who lost his East Renfrewshire seat to the SNP at last month’s General Election, was giving the final political speech of his career after standing down as leader on Saturday.

He said then that his future lay outside politics.

“There will be another referendum whenever the SNP can get away with it,” he told the audience.

“Why wouldn’t there? If you are an insurgent nationalist party with unprecedented power and with an absolute majority ... why wouldn’t you try and engineer a set of circumstances to get you another referendum?

“My frustration is that Cameron is so lame-assly dumb on it that he is set to stumble into it and give them the excuse to do it.”

Many critics believe Scottish Labour haemorrhaged support north of the Border after joining the Tories and Liberal Democrats in the anti-independence Better Together alliance in the referendum campaign.

And yesterday Murphy alluded to the issue when he admitted he would get “killed” for praising the Prime Minister, saying he thought he had enjoyed a “good referendum” last time round.

“I thought David Cameron actually had quite a good referendum,” he said. “He came fleetingly and when he came he did well.”

But Cameron’s decision to make an early statement following the result setting out plans for English votes for English laws had been an “astonishingly stupid” move, Murphy insisted.

“To me it showed he cares more about the longevity of his party than the stability of the Union.”

In his speech Murphy also called for Scotland to be “front and centre” of Labour’s 2020 election strategy and that to win at Westminster Labour needed to win support again in Scotland.

“Calculated purely on swing needed, the easiest two Labour targets to win back in Scotland are my old seat of East Renfrewshire and the seat of Edinburgh North and Leith ... but they are seats 26 and 44 in the simplest of UK target lists,” he said.

“The path to victory in middle England runs right through the heart of central Scotland.”

Murphy also offered a personal reflection on the consequences of the Blairite-Brownite split within Labour and of how his position as an ally of Blair had meant he had until recently no contact with Brown’s close ally Ed Balls, the former shadow chancellor.

Describing it as a “self-indulgent and self-destructive struggle”, Murphy said: “In the last two months of the election I have spoken more to Ed Balls than I did in the last two decades. I realised how wrong I had been. I had no closer support from any colleague during the election than Ed Balls. How wrong to wait until so late in the day to work together properly.”

In an earlier interview yesterday with the BBC, Murphy said Labour’s “catastrophic” election defeat was not just in Scotland, arguing that the party “cannot lose sight of the defeat in England”.