Ukip leader Nigel Farage has called on the Queen to intervene in the Scottish independence referendum.
Buckingham Palace issued a statement earlier this week saying the monarch was "above politics".
The palace said it was "categorically wrong" to suggest she would wish to influence the vote in next week's referendum.
But speaking on LBC radio, Mr Farage said it could be argued that the Queen had a responsibility to speak.
The Ukip leader, who will be holding a rally in Glasgow later, said: "I completely understand her wanting to keep out of politics and she has done it brilliantly over 60 years.
"But there are times where if the United Kingdom, over which she is the monarch, is threatened itself, it might be right for her to say something.
"Let's say we got to this Sunday and it was still 50/50 in the polls, I personally think she should say something."
Mr Farage said there was a precedent for the Queen intervening because she addressed independence in her Silver Jubilee speech in 1977.
"She said very clearly I am the Queen of the entire United Kingdom," he said.
"So she said it before and it might be handy if she said it again."
Sources in Better Together, which is campaigning for a No campaign, dismissed Mr Farage's call for the Queen to intervene as "absolutely preposterous".
Earlier this week Scotland's First Minister Alex Salmond said the Queen "will be proud" to be the monarch of an independent Scotland.
The palace later insisted the referendum was "a matter for the people of Scotland".
A spokesman said: "The sovereign's constitutional impartiality is an established principle of our democracy and one which the Queen has demonstrated throughout her reign.
"As such the monarch is above politics and those in political office have a duty to ensure that this remains the case.
"Any suggestion that the Queen would wish to influence the outcome of the current referendum campaign is categorically wrong."
The BBC's royal correspondent Peter Hunt said he understood that the comments were made in response to calls for the Queen to speak out in favour of the union and not in response to Mr Salmond's remarks.
Under the plans for independence outlined in the Scottish government's white paper, the Queen would remain head of state.
BBC assistant political editor Norman Smith said sources in the Better Together campaign strongly criticised Mr Farage for suggesting the Queen should make a public statement of support for the union.
They insisted it would not be appropriate for the Queen to become involved.
No campaigners have urged the UKIP leader - whose trip to Scotland last year ended with him barricaded inside a pub to escape protesters - to stay away for fear he will alienate traditional Labour supporters.
But he insisted he intends to press ahead with an address to supporters in Glasgow, and said he had "absolutely no intention of being incendiary at all".
Mr Farage told BBC Radio Four that the Scottish people were being sold a "false prospectus" by the campaign for independence.
He said Scotland would not be independent and self-governing if it signed up to the EU.
The UKIP leader said that the currency was Alex Salmond's 'Achilles heel'
And he claimed Scotland would have to make a commitment to join the euro if it signed up to join the EU.
Mr Farage, whose party got 10% of the vote in Scotland and gained an MEP at the European Parliament elections earlier this year, said: "People say 'of course Scotland is not as Europsceptic as England'. I tell you something, it is not that far behind."
He added: "If the Scottish people want to separate from Westminster, want to be part of the EU state, want the euro as their currency, then voting Yes is fine for them.
"But my job today is to say 'hold on, you are being sold a false prospectus'."
The SNP wants to keep the pound in the event of independence in a currency union with the rest of the UK.
A spokesman for Yes Scotland said: "The pound is Scotland's currency every bit as much as the rest of the UK's, and it will remain our currency after independence."