Tony Blair has called for campaigners for Britain to stay in the European Union to make the case with "passion, vigour and determination".
The former prime minister said the UK's destiny is to "lead in Europe" and warned that Brexit would cause economic instability and "damage fundamentally" the interests of the British people.
Mr Blair told the BBC Radio 4 Today programme: "The question is, what is in the interests of the people?
"And I would like to see the pro-European side get out there with a bit of passion and vigour and determination and stand up for what we believe.
"And what we believe not just as a matter of economic realism, but as a matter of political idealism."
His intervention comes as the Remain camp has been branded "Project Fear" by opponents, while Labour leader Jeremy Corbyn has been accused of being conspicuously absent from the campaign trail.
Mr Blair admitted he was "concerned" by the fervour and enthusiasm displayed by the Brexit campaign, and said more passion should be shown by pro-Europeans.
He said: "I think in the end this referendum will be won for those that see Britain remaining part of the European Union.
"But you can't have a referendum like this, especially with the fervour on the anti side, and not be concerned.
"So I am concerned, but I believe in the end we will vote to stay."
But Mr Blair, who remains a hugely divisive figure nationally, admitted he is not the right man to take centre-stage in the campaign to stay in the EU.
He said: "I don't know whether it is the right time for me on the campaign trail - that carries with it negatives as well as positives.
"But I think it is certainly time for people to argue this case for Europe with some passion."
Displaying his frustration with discussions about Brussels, the former premier said Britain's "destiny" is to lead in Europe and warned that leaving risked weakening the economy for no good reason.
Laying out a vision where Britain was at the heart of the EU, he said: "Britain has got a great opportunity to lead in Europe.
"Britain is a great country, it's a strong country, it's a strong economy - person for person it is in the Premier League of systems."
He added: "Our destiny as a country is to lead in Europe, and we can and we should.
"And once this is out of the way, with some strong leadership in our own country, we will.
"But we have got to realise how fast the world is changing, how important this relationship is, and the massive instability that is going to come for no good purpose if we take the wrong decision."
He rebutted claims that the "political elite" are pro-European while the public are more sceptical, pointing out that many leading figures in politics and media are leading the Brexit campaign.
Britain "has gained enormously" from being part of the EU, he said.
"And the world that is developing today, it is not to satisfy some elite that we should be part of the biggest political union and biggest commercial market in the world.
"It is precisely to satisfy the interests of the people, those interests that will be damaged fundamentally - not the elites, by the way, supporting this case to get out of Europe - the people are going to be damaged by the instability and the economic difficulty that is going to be consequent from the decision to withdraw."
And he issued a rallying cry for the centre-ground of British politics to reassert itself.
He said: "At some point the political class as a whole has got to get up and stand up for itself.
"And the centre-ground in particular has got to get some more muscularity in its position."