Devolution legislation is to be changed to make it "crystal clear" that the Scottish Parliament is a permanent part of the UK's politics, David Cameron has pledged.

The Prime Minister used the first anniversary of the independence referendum to confirm his government would make amendments to the Scotland Bill to achieve that.

That legislation will make Holyrood "one of the most powerful devolved parliaments in the world", Mr Cameron said.

The UK Government is to bring forward an amendment to the Bill aimed at strengthening the language about the permanence of the Scottish Parliament and the Scottish Government.

The changes will also put in legislation that Holyrood can only ever be abolished if this is backed by the Scottish people in a referendum.

Mr Cameron said: "One year ago, Scotland's majority spoke. More Scots voted to keep our kingdom united than have ever voted for any party in any election in Scottish history.

HeraldScotland: David Cameron

"They voted decisively for a powerful Scottish parliament within a strong and secure United Kingdom. We listened.

"So, let me be crystal clear: Scottish devolution is woven into the very fabric of our United Kingdom.

"We will table an amendment to the Scotland Bill so there is absolutely no doubt: Holyrood is here to stay."

In last year's referendum, 55% of voters backed remaining in the UK, with 45% in favour of independence.

But May's general election saw the SNP win all but three of the Scottish constituencies while two opinion polls this month have suggested a majority of people are now in favour of independence.

Mr Cameron, however, said: "Alex Salmond, Nicola Sturgeon and I signed the Edinburgh Agreement which pledged we would all respect the outcome of last year's momentous vote.

"We all agreed - as do the Scottish public - that the independence referendum should be a 'once-in-a-generation' or a 'once-in-a-lifetime' event. So, now it is time to move on."

He added: "Some may want to obsess about separation.

"But I am focused on delivering devolution so that the debate can move on from what powers the Scottish Parliament should have, to how they are used to better the lives of the people of Scotland.

"Today, on the anniversary of that historic vote, let me be repeat: We are delivering a new, accountable and permanent Scottish Parliament. Holyrood will be one of the most powerful devolved parliaments in the world."

Speaking on BBC Radio Scotland, First Minister Nicola Sturgeon said: "I welcome anything that strengthens the Scotland Bill but I think what the Prime Minister has indicated today is actually an admission that the Scotland Bill doesn't live up to the proposals in the Smith Commission and doesn't implement the vow that was made in the closing days of the referendum campaign.

HeraldScotland: First Minister Nicola Sturgeon

"We've seen a poll in the last few days that says only 9%, less than one in ten of people in Scotland, think the vow is being delivered, so I welcome the amendment that has been announced by the Government today but I think they have to go a lot further before they can get anywhere near to the position of saying that they are delivering on the promises they made."

She added: "I welcome anything that says our Parliament is permanent. I think probably most people across Scotland would have assumed that the Scottish Parliament was permanent anyway and would never have imagined that a UK government, although constitutionally it is able to, that a UK government would try to abolish it, but anything that strengthens the Scotland Bill I welcome."

She said that the Scotland Bill doesn't live up to the Smith Commission in various areas including welfare and the Crown estate.

She told the programme: "Today I welcome what's been said but it's only one step in a long road that I think has to be travelled to make the bill that is before the House of Commons representative of what people were promised."