The British government is examining plans to designate the Scottish military base that houses the Trident nuclear deterrent as sovereign United Kingdom territory if the people of Scotland vote for independence in next year's referendum.

In a move that sparked an angry reaction from the SNP, which vowed to rid Scotland of nuclear weapons as quickly as possible after a yes vote, the government is looking at ensuring that the Faslane base on Gare Loch in Argyll and Bute could have the same status as the British sovereign military bases in Cyprus.

The move would be designed to ensure that the Trident fleet would continue to have access to the open seas via the Firth of Clyde. Under Britain's "continuous at sea deterrent", at least one Vanguard submarine armed with 16 Trident nuclear missiles is on patrol at sea at any one time.

The warnings over Faslane come as the British government issues stark warnings to the people of Scotland about the dangers of independence.

Angus Robertson, the SNP leader at Westminster, said: "This is an extraordinary attempt by Westminster to bully Scotland. Neither the people nor parliament of Scotland want nuclear weapons dumped here, and we are clear that Trident would have to be removed as quickly as possible. Only a yes vote next September will empower Scotland to get rid of Trident, and the money saved help build a fairer society and stronger economy."

But William Walker, professor of international relations at the University of St Andrews, told the Guardian: "Threats and counter threats are going on. The risk the government in London is taking – and I think they are waking up to this – is that it all seems like scaremongering."

The Ministry of Defence is officially working on only one option for the Faslane base ahead of next year's Scottish independence referendum – a defeat for the SNP, thereby guaranteeing the survival of the base that has housed the nuclear deterrent since the Polaris era in the 1960s. An MoD spokesperson said: "We are confident that the Scottish people will vote to remain a part of the United Kingdom."

But MoD officials are starting to examine a two-stage process to ensure that Britain could continue to station the Vanguard submarines at the deep-water Faslane base and store the nuclear warheads at the nearby Coulport base on Loch Long.

The British government would first tell the Scottish government after a yes vote that it would cost tens of billions of pounds over many years to decommission the Faslane base and to establish a new base in England or Wales to house the nuclear fleet.

These costs would have to be factored into severance payments negotiated with the Scottish government before full independence is declared around two years after the referendum.

Philip Hammond, the defence secretary, gave a taste of the costs when he told the house of commons defence select committee last week: "It would cost a significant amount of money."

As an alternative, the Scottish government would be told it could reduce the costs to Edinburgh if it agreed to allow Faslane to be designated as sovereign UK territory along the lines of the Akrotiri and Dhekelia sovereign base areas (SBAs) in Cyprus.

The base could be designated an SBA for an initial period of 10 years – to allow for decommissioning – if the Scottish government rejects out of hand calls to allow Trident to be based in Faslane. If the Scottish government were to accept that Trident should remain in Scotland then a longer lease would be negotiated.

One defence source said: "It would cost a huge amount of money, running into tens of billions of pounds, to decommission Faslane. Those costs would be factored into any negotiations on an independence settlement. The sovereign base area is an option. It is an interesting idea because the costs of moving out of Faslane are eye-wateringly high."

An MoD spokesperson said: "No contingency plans are being made to move Trident out of Scotland. The scale and cost of any potential relocation away from Faslane would be enormous."

Sir Nick Harvey, the former Liberal Democrat armed forces minister, said designating Faslane as sovereign UK territory would be the only practical way of ensuring Britain retained a nuclear deterrent.

"If the Scots were to insist on us leaving it would sour the relationship on the broader canvas," he said. "I think the most practical and likely outcome would be a Cyprus-type arrangement.

"No doubt they would extract a financial price for that. But at the point the UK and Scottish government sit across the table looking at eachother the UK government will only have a certain amount of money at its disposal. If the Scots demand a high price for satisfaction on the nuclear front there would be that much less money in the UK government's pocket for all the other items which will be on the agenda."

Harvey raised the prohibitive costs of relocating the nuclear deterrent – and the need for Britain to retain control of the Faslane base – when he appeared before the Scottish affairs select committee as a minister last year.

Harvey said that the two original alternatives to Faslane – Falmouth harbour and Milford Haven – would involve very high costs because they have been heavily developed since the 1950s. He said: "I don't think relocating the base anywhere else is, in all honesty, viable. It is not practically impossible but it is not realistically viable."

Robertson said: "A key argument for independence is that Scotland will no longer have to pay for nuclear weapons that we do not want. A no vote, by contrast, means a new generation of nuclear weapons on the Clyde for another 50 years.

"Last October, Westminster's Scottish Affairs Committee report said that Trident 'could be disarmed within days and removed within months'. Former UN weapons inspector Hans Blix has urged the UK Government to scrap Trident. It is a matter for Westminster what to do with Trident after a Yes vote and to pay for it – but rather than dump it elsewhere it may well be that most people in the rest of the UK would regard Scottish independence as an opportunity to follow Mr Blix's wise advice and get rid of nuclear weapons altogether, saving £100 billion in the process."

Sir Menzies Campbell, the former leader of the Liberal Democrats who has conducted a review of Trident for his party, warned of a backlash.

"To seek to impose a financial penalty on an independent Scotland in relation to the decommissioning of Faslane might be seen as undue pressure and could easily play into the hands of the SNP," he said.

""The straightforward answer to all of these issues is to ensure that the referendum is won by those who believe that the United Kingdom should be preserved."

But Campbell said that the Scottish government may find that it would face pressure to be accommodating to the UK government if it seeks to join Nato. The former Lib Dem leader said: "As the debate continues over Trident the illogicality of the SNP position becomes yet more apparent. It seems extraordinary to be opposed in principle to nuclear weapons but to wish to join an alliance whose strategic concept provides that deterrence should be by way of conventional and nuclear means. The SNP answer to this point is a bland assumption that an independent Scotland would merely, by applying, be entitled to the dispensation enjoyed by Norway. But Norway was a founding member of the alliance. The fact that a dispensation in relation to nuclear matters has been allowed to Norway cannot be a guarantee that a new applicant would be allowed the same privileges."

This view was echoed by Jim Murphy, the shadow defence secretary. He said: "This underlines the uncertainty of Scottish independence. Major questions remain unresolved by the SNP who have a defence policy based more on faith than fact.

"The best way to protect the Scottish defence industry and national interest is for Scotland to remain part of its primary defence alliance: the UK. The SNP are confused on nuclear defence. They seek the security of the NATO nuclear alliance without fully accepting the NATO Strategic Concept. The SNP want to downgrade Scotland's role in the world and our strength at home. The UK provides Scotland not just with protection but influence."

The MoD's work will have added significance because a long-awaited government review is expected to conclude next week that a modified version of Trident remains the cheapest option.

The review, chaired by the Treasury's chief secretary, Danny Alexander, is expected to conclude that the options of putting Trident missiles on modified Astute-class submarines or putting nuclear warheads on cruise missiles on Astute submarines are too expensive.

Amending Trident could also put Britain in breach of its obligations under the nuclear non-proliferation treaty which commits Britain to reducing its nuclear arsenal. Varying warheads would count as a new development.