Media playback is unsupported on your device Media caption Jim Sillars says Scotland should have its own currency as Alex Salmond continued to claim sterling as Scotland's pound

Scottish First Minister Alex Salmond has insisted Scotland will retain sterling under independence, in the face of continued opposition criticism.

He said a formal currency union with the rest of the UK was the best option, saying: "It's Scotland's pound and we are keeping it."

The first minister's opponents earlier delivered a giant pound coin to his official residence.

The Better Together campaign said it highlighted a lack of currency answers.

Mr Salmond said that if UK politicians refused to share the Bank of England, Scotland would not have to share the national debt. This would lead to George Osborne and Ed Balls having to tell the people of England they would give the Scots "a present of £5 billion a year," he claimed.

Meanwhile, Jim Sillars, a key "Yes" campaigner, said an independent Scotland should have its own currency, telling the BBC: "Alex Salmond is not the leader of the 'Yes' campaign."

The Scottish government previously set out its currency union plan ahead of the 18 September independence referendum, but the leaders of Westminster's main parties have said they would not back such a deal, and have urged Mr Salmond to come up with a currency "Plan B".

Mr Salmond set out his position during question time at Holyrood, in the face of criticism from Scottish Labour leader Johann Lamont.

"The reason we are keeping the pound in a currency union, and the reason we are so unambiguous about it, is because we are appealing to the greatest authority of all, that is the sovereign will of the people of Scotland," said the first minister.

Image copyright Labour Party Image caption Scottish Labour deputy leader Anas Sarwar called at Bute House, the first minister's official residence

"After a 'Yes' vote in the referendum, I am sure that Johann Lamont will be among those who accept that sovereign will of the people of Scotland.

"It is Scotland's pound. It doesn't belong to George Osborne, it doesn't belong to Ed Balls. It's Scotland's pound and we are keeping it."

Ahead of first minister's questions, Scottish Labour's deputy leader, Anas Sarwar, delivered the giant pound coin to Bute House, in Edinburgh, claiming Mr Salmond was not able to give a "straight answer" on currency.

"Scots deserve to know what his plan B is," said the Labour MP.

"They want to know what currency they'll get their wages in, what currency they'll get their pensions in, what they'll use to get the weekly shop, how it will affect their mortgages and car loans and what our businesses will trade in."

Mr Sillars, a former SNP deputy leader, said there had to be an answer to Westminster's refusal to a currency union.

Image copyright Yes Scotland Image caption Nicola Sturgeon launched the poster campaign alongside Yes Scotland chairman Dennis Canavan

"We have a viable alternative, and it's a Scottish currency with our own central bank, printing Scottish notes which we will peg one-to-one with Sterling, so there's no difference whatsoever," he told the BBC.

Mr Sillars argued Scottish currency would be "strongly underpinned" because Scotland exported more than it imported, which would bring in foreign currency reserves.

He added: "Alex Salmond is not the leader of the 'Yes' campaign, and that's something the media hasn't understood."

Mr Sillars said Mr Salmond's role as first minister was "important", adding that his government had published a fiscal report advocating a Sterling union, but also a "Plan B, a Plan C and a Plan D".

"Plan B. separate Scottish currency, perfectly normal answer," said Mr Sillars, adding: "It happens all over the world, why shouldn't we do it?"

Meanwhile, Deputy Scottish First Minister Nicola Sturgeon launched a new poster campaign, arguing that a vote for independence was Scotland's "one opportunity" for a more prosperous economy.

She unveiled it in Edinburgh with Dennis Canavan, chairman of the Yes Scotland campaign for independence, who has also voiced support for an independent Scotland having its own currency.