The best result Labour can achieve in the General Election is to be a "sizeable opposition" to the Conservatives, former chancellor Alistair Darling has said.
Twenty years after Tony Blair swept to power with a landslide vote, Mr Darling appeared to rule out the prospect of a Labour victory.
He said: "It's important we get the best possible result for the country - that means having a sensible sizeable opposition that can actually make a difference."
Mr Darling spoke while campaigning in Edinburgh South - the seat held by Labour's one remaining Scottish MP Ian Murray.
The former chancellor, who also headed the campaign to keep Scotland in the UK in 2014, stressed the importance of getting "people like Ian returned at the next election so we've got decent people arguing against an ever more extreme, bleak view of what might happen".
He argued that politics in has "skewed to the right" under the Conservatives, leaving so-called Middle Britain - whose votes Mr Blair captured - unrepresented.
But with Brexit looming, Mr Darling said there was a need for "sensible" politicians making the case for the UK to continue to have a relationship with the European Union after it leaves.
Asked if he endorsed Labour's left wing leader, Jeremy Corbyn, Mr Darling said: "He is the leader, he is the leader right up to the General Election.
"My view is we need to get on, we're fighting a general election campaign, you know leaders come and go."
He added: "There's no question he's the leader, it's for him to convince people in the next six weeks and voters will make of it what they will."
Mr Darling, who stepped down as the MP for Edinburgh South West just before the 2015 election, said: "One of the problems we have in the UK is for a long time the middle, sensible voice, middle Britain if you like, was unrepresented and the entire political debate has been skewed to the right.
"In many cases it's been hijacked by people who take a very extreme and narrow view of our relationship with the rest of Europe.
"And we need to have a balanced view. Jobs, prospects for the future, depend on us having a sensible view.
"That's why it's important you have a strong voice in the House of Commons making that point."
He added: "I've always thought Theresa May's main problem in the House of Commons is not actually the Remainers, they are the Brexiteers, who disposed of three other leaders of the Tory party within recent memory, and I'm sure she's very conscious of the fact that left to their own devices they might do the same again.
"That's why you need sensible people in the House of Commons who take a different view."
While Labour's fortunes have been on the wane, Mr Darling said when he was first elected as an MP 30 years ago he "would have hardly believed we would win with a thumping landslide majority 10 years later".
He said: "In politics things change, fortunes go up and down. What's interesting when you look at politics today, it is increasingly divided, not just in Scotland or the UK but in other parts of the world along nationalistic lines."
He welcomed Mr Blair's return to the political front line, saying the former prime minister should do "what he's been doing over the last few weeks, providing a sensible voice on where our relationship should be with the rest of Europe".
Mr Darling said: "Because our relationship with Europe is the big issue that's facing this country at the moment, what comes out of the Brexit negotiations will define the future for the next few generations, never mind the next few years.
"And what he is saying is, geographically as well as politically, we're always going to be close to Europe, we always have been, and we need to have a sensible relationship."
With the SNP having been in power for 10 years now in Scotland "there's a warning to all politicians - there comes a point where the voters actually notice you've been in power and, secondly, you haven't done very much with it."
But he stressed that the "big issue in this election is this party's future post the Brexit referendum".
The former chancellor said: "We now face a situation where we have a very, very uncertain future following the Brexit vote. It wasn't the result I wanted but democracy means that that is where we are.
"I think there is a very real risk that the debate in this country is going to be hijacked by people who take a very extreme, bleak and narrow view of what this country can be. And that's why I want to see as many Labour MPs as possible in the House of Commons.
"I think the majority of people in this country, in Scotland, they don't want another referendum and nationally they want to see a sensible relationship with Europe."
He added: "We decided three years ago very clearly that we wanted to stay in the United Kingdom. We were told it was a once-in-a-generation choice then, and many people believed that was the case. We don't want to reopen that."
If there is a second vote on Scottish independence, he ruled out taking a lead role again for the pro-UK campaign.
"It's for another generation to take the lead. I've stepped well back from front line politics now," Mr Darling said.
"It's for others to do that. But I don't actually think the majority of people in Scotland want another referendum. It's very clear that even people who voted Yes in 2014, they don't want one."