The battle for Scotland's future shifted to voters' TV screens for the first time on Tuesday when the leader of the pro-independence campaign debated the leader of the pro-U.K. campaign in a U.S.-style debate ahead of a historic referendum.

Scots will decide on Sept. 18 whether to remain part of the United Kingdom or to break their 307-year union with England and strike out alone with opinion polls showing most voters will reject independence.

However, Alex Salmond, Scotland's nationalist leader, is hoping he can turn the tide in the final weeks of the campaign by drawing on his widely recognized rhetorical skills.

'No one, absolutely no one, would do a better job of running Scotland than the people who live and work in Scotland.' - Alex Salmond, Scottish nationalist leader

During Tuesday's TV debate, Salmond argued that an independent Scotland could build a fairer and richer society.

The British government spent far too much on nuclear weapons, he said, but had failed the people of Scotland while imposing taxes. Salmond has promised to rid Scotland of nuclear arms if Scotland becomes independent.

"My case this evening is simple: No one, absolutely no one, would do a better job of running Scotland than the people who live and work in Scotland," Salmond told an audience in front of a screen bearing Scotland's white and blue flag.

"On the 18th of September we have the opportunity of a lifetime — we should seize it with both hands," said Salmond.

Surveys consistently show opponents of independence holding on to a substantial lead over those who want to end the union with England, though as many as a quarter of Scotland's 4 million voters have yet to decide.

A poll from Ipsos Mori released as the TV debate commenced showed support for independence had risen to 40 per cent, up 4 points since a similar poll in June and the highest support that the pollster has yet recorded for the "Yes" campaign.

However, other polls have suggested that the "Yes" campaign stalled at the end of March and Tuesday's poll found that 54 per cent were set to reject independence, unchanged since June, while 7 per cent of the electorate were still unsure how they would vote — a 3 point fall.

'No going back'

In the debate, Salmond, leader of the pro-independence Scottish National Party, was pitted against Alistair Darling, head of the "Better Together" anti-independence campaign.

"If we decide to leave, there is no going back, there is no second chance. For me the choice is very very clear: I want to use the strength of the United Kingdom to make Scotland stronger," said Darling.

Scottish independence Alistair Darling

Alistair Darling, head of the 'Better Together' anti-independence campaign, argued Scotland is stronger as part of the United Kingdom. (David Moir/Reuters)

"We can have the best of both worlds with a strong Scottish parliament with full powers over health, over education and with more powers guaranteed because a vote to say no thanks to the risks of independence is not a vote for no change."

Darling was finance minister in the last British Labour government and his party commands wide respect in Scotland.

In his critique of the nationalist case, Darling, at times raising his voice, focused on economic arguments, particularly what plans Salmond had for its post-independence currency and its future revenues.

After pushing Salmond on how an independent Scotland could keep the pound, given that the British government had excluded a currency union, Darling repeatedly asked: "What is plan B?"

"I am in favour of keeping the pound sterling," Salmond, dressed in a grey suit, said, after he was booed by at least one member of the audience.

Debate broadcast only in Scotland

Darling was spoken over by at least one member of the audience and the moderator of the debate asked the audience to respect the debate. Both men interrupted each other at times.

Sometimes reading from notes and quoting news reports, Salmond branded the "No" campaign as "Project Fear" and complained about its tactics.

SCOTLAND-REFERENDUM/

Scotland is set to hold its independence referendum on Sept. 18. (David Moir/REUTERS)

He also accused Darling, a left-wing politician, of being allied with ministers belonging to right-leaning Prime Minister David Cameron's government, which he said wanted to lead Britain out of the European Union.

"I want Scotland to stay inside the European Union," said Salmond.

Cameron says he wants to keep Britain inside a reformed EU.

Salmond's supporters argue that Scotland, which has its own parliament and judicial system but lacks substantial tax-raising powers, would be freer, better governed and richer on its own.

The "No" campaign argues Scotland would be unable to keep the British pound, that tens of thousands of jobs in the defence and financial sectors would be at risk, and that an independent Scotland might find it hard to rejoin the European Union.

Only Scots living in Scotland can vote in the referendum and only viewers north of the border with England were able to watch the debate on terrestrial TV.

An affiliate of British broadcaster ITV showed the debate in Scotland. In the rest of Britain, it broadcast a gardening show at the same time. Some Scots living in England tried but failed to watch the debate on the broadcaster's Internet site.

Earlier on Tuesday, in a move widely seen as an attempt to undermine Salmond, Britain's three main political parties all said they would seek further powers for Scotland in the event of a "No" vote when it came to tax raising and social security.