The political union with the rest of Britain "imperils" Scotland's future and must be changed as a matter of urgency, the First Minister has said.

Leaving the UK would end the "democratic deficit" which has led to renewal of Trident, the bedroom tax and the privatisation of the Royal Mail being "imposed" on Scotland, Alex Salmond said.

If the country votes Yes in next year's independence referendum it would continue to benefit from being in other unions such as the European Union (EU) and a currency union with the remainder of the UK, he said.

The First Minister spoke out as he addressed workers at Nigg Energy Park on the Cromarty Firth in the Highlands.

The speech, the first of a series he will make over the summer, highlighted the six unions that "govern our lives today in Scotland".

An independent Scotland would continue to be in five of these unions: the EU, a currency union, the Union of the Crowns allowing the Queen to remain the monarch of Scotland, a defence union through membership of Nato and a social union between the people of the UK, Mr Salmond said.

The Scottish Government would need to negotiate a currency union, EU membership and membership of Nato in the event of a Yes vote in the referendum, to be held on September 18 next year. But the political union with the rest of the UK must be ended, Mr Salmond insisted.

"The political union does not work for Scotland any more. It holds Scotland back and imperils our future. It will not bend and it will not change of its own accord. So we will, we must, change it.

"We must address and fundamentally change the political and economic union as a matter of urgency. This political union is only one of six unions that govern our lives today in Scotland, and the case for independence is fundamentally a democratic one.

"A vote for independence next year will address the democratic deficit which sees policies like the punitive bedroom tax, the renewal of Trident or Royal Mail privatisation imposed on Scotland against the wishes of Scotland's democratically elected representatives.

"But that will still leave five other unions intact. We will embrace those other unions while using the powers of independence to renew and improve them."

He insisted: "We will remain members of the European Union but with a seat of our own at the top table and without the uncertainty of a referendum on membership, as proposed at Westminster.

"We will still be members of Nato, co-operating with our neighbours and friends in collective security. But we can still decide not to be a nuclear power, like 25 out of 28 current members of Nato.

"We will be part of a currency union with the rest of the UK but we will finally have the full taxation powers we need to promote jobs and investment."

While Scotland would retain the Queen as monarch after independence, he said: "We will adopt a new constitution, written and endorsed by the people, asserting rights as well as promoting liberties and enshrining the ancient Scottish principle that ultimate sovereignty rests with the people."

The social union that "unites all the people of these islands" did "not rely on the choices made by politicians and parliaments".

After independence "people in England will still cheer Andy Murray, and people in Scotland will still support the Lions at rugby".

People would still be able to move about the UK freely for work, rejecting claims made by former chancellor Alistair Darling that being part of Britain provides people in Scotland with greater opportunities.

Mr Darling, leader of the Better Together campaign to keep Scotland in the UK, argued: "The complete freedom of movement that we enjoy provides immediate opportunities for young people to have careers that span the whole of the UK. Our young people can take up jobs anywhere in the UK with no barriers or administrative difficulties."

But Mr Salmond said: "People will still change jobs and move from Dundee to Dublin, or from Manchester to Glasgow. With independence, we will continue to share ties of language, culture, trade, family and friendship. The idea that these ties are dependent on a Parliament in London are and have always been totally nonsensical."

The powers of independence could boost Scotland's economy, create jobs and "build a more equal and more prosperous society".

The Scottish Government is only able to do so much to mitigate the impact of Westminster cuts, he said.

"Using the powers of the Scottish Parliament, we have cushioned 500,000 Scots against London cuts to council tax benefit but we cannot stop more than 82,000 households, including over 15,000 families with children, from having the bedroom tax inflicted upon them.

"In recent years, in the face of Westminster's austerity agenda, we have led the rest of the UK on attracting inward investment, done all we can to protect capital spending and prioritised youth employment so that we have the sixth-best rates in Europe.

"But we lack the key economic tools that could be used to boost Scotland's economy further, create more jobs and help build a more equal and more prosperous society.

"We have up to a quarter of the European Union's offshore renewable energy potential, but no control over the electricity market reform process which has spread such uncertainty over renewables.

"We have the major share of the European Union's oil production. But we had to watch when a number of UK tax changes in the last decade delayed investment in our offshore fields.

He went on: "We can't clear the country of nuclear weapons. We can't even prevent fuel poverty in energy-rich Scotland.

"With devolution, we can mitigate the impact of some Westminster decisions. But it is mitigation, and no more."

A Scotland Office spokesman said: "Devolution continues to deliver for Scotland, giving the best of both worlds: a strong Parliament in Scotland which is receiving more powers through the Scotland Act 2012, coupled with the UK Parliament giving Scotland an influential voice within the UK family.

"The devolved powers at Holyrood give the Scottish Government a huge amount of flexibility to set policies that benefit the lives of people in Scotland.

"There is a strong positive case for Scotland staying within the UK, from a single market for trade to our influence in the world and the advantages from being a single UK, whether that is subsidies for renewable energy in Scotland or an economy which can manage volatility and risk.

"The referendum raises many questions about Scotland's future. We are answering them through the Scotland analysis papers and in other ways. The Scottish Government must provide its own answers on how independence would affect life in Scotland on a range of issues from pensions, currency and welfare spending to the set-up costs of creating a new state from scratch."

A Better Together spokesman said: "Alex Salmond wants us to believe that if we vote for separation then somehow everything will change. But nothing will change. It is absolute rubbish.

"He wants to break up the United Kingdom and is using every cynical ploy open to him to try and achieve that. At a time when we should be breaking down barriers, he wants to put new ones up. When we should be looking for ways to bring people together, he is dreaming up ways of forcing them apart. When we ought to be celebrating everything that unites us as citizens, he is looking for ways to give air to grievances and to blame everything on someone else.

"His vision of our country's future is not about what is best for our young people, our public services and our pensions. It is only about realising his long-held ambition of separating Scotland from our closest neighbours. We will work every day between now and the vote to ensure that we stay united with our friends, families and workmates."

Liberal Democrat leader Willie Rennie also hit out at Mr Salmond.

"The First Minister will say and do anything to break up the UK even if it means advocating the continuation of several unions with the UK from the currency union to the social union," he said.

"Yet he can't guarantee all of it, as if we slam the door in the face of the United Kingdom they may just lock it from the other side. They might not agree to Scotland's every demand.

"The best way to secure our unions with the UK is to support home rule in a federal UK offered by the Liberal Democrats. With a massive transfer of tax and constitutional power, we can control our destiny on the domestic agenda whilst enhancing our place as equal partner in the United Kingdom."