The British Government's approach shows power "really lies" in London at the expense of devolved administrations in Edinburgh and Cardiff, Nicola Sturgeon said.
She made the remarks in a speech in the Welsh capital, suggesting Scottish independence would stop parts of the UK having to compete for shares of "our own money".
"Those opposed to independence used to claim that the UK, as it currently stands, is an equal partnership of nations and of people," she said in the Wales Governance Centre annual lecture.
"But in its attempts to scare, and now threaten, voters in Scotland, the No campaign is destroying the very idea that the UK is an equal partnership.
"That notion is being torn apart on an almost daily basis.
"The leaders of the No campaign are going out of their way to demonstrate where they think power really lies.
"As far as the UK Government is concerned, power rests with one party in this relationship: with Westminster.
"And we have discovered that as far as Westminster is concerned, people in Scotland have fewer rights than most of us thought."
She referred to heated political rows on what currency Scotland could use and what institutions and organisations it could hold on to.
"As long as we stay with Westminster, the UK Government is saying they will allow us to benefit from the institutions we have paid for," she said.
"But if we vote Yes they will decide what we are, and what we are not, entitled to receive."
She focused on Scottish independence, but frequently gave her view on how it may affect Wales.
"I believe that Scottish independence will not only benefit Scotland, but also the other nations of the British Isles and the relationship between us," she said.
"The social union that exists between us is strong and I believe independence for Scotland can make it even stronger."
She continued: "An independent Scotland will still be part of the British Isles and a member of the British-Irish Council - which is, of course, headquartered in Edinburgh. And, as an independent member we could, when circumstances demand, be an even more powerful ally of Wales than we are able to be just now."
Independence will help Wales win a better financial deal, she argued.
"That would be much better than having Scotland and Wales set against each other in lobbying Westminster for fairer allocations of our own money.
"Your job in Wales is to argue for your best interests - and I respect that - but reform of the Barnett formula after a No vote holds real dangers for Scotland. That is why a Yes vote is so important for Scotland."
She added: "I don't want Scotland, as a country, to have to lobby Westminster for a fair allocation of our own money and be in competition with Wales in doing so.
"That is the opposite of strengthening devolution. It is the opposite of the financial responsibility that I want us to have. But it is what will happen if we vote No."
Ms Sturgeon confirmed that an interim written constitution will be included in the draft Scottish Independence Bill, which is due to be published before summer.
"The Bill will set out an interim constitution for Scotland - founded on the principle of the sovereignty of the people - and outline the participative and collaborative process by which Scotland, as an independent country, will prepare its permanent written constitution," she said.