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.”