ALEX Salmond will today highlight the success of Scotland's "partial independence" since 1999 as he seeks to step up the campaign for a Yes vote in next year's referendum.

The First Minister will use his keynote speech at the SNP Spring conference in Inverness to explain what he called "the why of independence".

He will highlight the Iraq war, Trident nuclear weapons on the Clyde and North Sea oil as reasons for leaving the UK.

Mr Salmond will say: "In six years, we have taken trust in the Scottish Government to a high of 71%, four times more than trust in Westminster.

"With the partial independence the Scottish Parliament has in health, education, justice, business support and social services, we have achieved much – and with the full measure of independence we get by voting Yes, we will be able to achieve much more for Scotland."

Mr Salmond will address the party faithful two days after unveiling September 18, 2014 as the referendum date.

Yesterday, he welcomed the party's 25,000th member, 17-year-old Elysee Ahmed-Sheikh.

Ahead of his speech, the SNP leader said: "Conference will set out the 'why of independence' to the people. What won't happen in an independent Scotland will be getting dragged into illegal wars, having Trident nuclear weapons dumped on the Clyde for another 50 years, or the imposition of bedroom taxes.

"And what will happen will be the mobilisation of the human and natural resources of Scotland to build a prosperous economy and just society."

He is expected to highlight Holyrood policies including free personal care, the abolition of university tuition fees and increased police numbers.

As delegates gathered, separate polls showed strong support for handing Holyrood more powers and high – though falling – levels of satisfaction with the SNP Government.

A YouGov poll for the party found 52% of Scots believed the Scottish Government should be responsible for all tax and spending decisions in Scotland.

It also showed 53% thought the Scottish Government would be best at deciding welfare and pensions policy for Scotland.

Polls asking about more powers traditionally produce higher levels of support than those asking directly about independence, support for which is at 33% compared with 52% opposed and 15% undecided, according to the most recent survey.

Finance Secretary John Swinney, who is due to address the conference tomorrow, said: "There is a clear majority support for the key decisions about Scotland to be taken right here in Scotland. This is a big blow to the No campaign."

Meanwhile, an Ipsos MORI poll found 53% are satisfied with how the Scottish Government is running the country, down one point since October, compared to 41% who are dissatisfied, up two.

The net approval rating of +12 points was down three points overall. Approval among men, at +21, is higher than among women, at +4.

Overall, the Scottish Government's score contrasts markedly with the UK Government's net approval rating of -41 among voters across Britain.

Pollster Christopher McLean said: "Satisfaction is particularly high among men and young people, which reflects patterns in voting intention for the SNP and support for independence. However, the relatively low satisfaction among women is further evidence that the SNP need to do more to appeal to female voters."

A Scottish Labour spokesman said: "To describe devolution, which has been the settled will of the Scottish people since 1999, as partial independence is another example of the SNP misrepresenting people's votes.

"Alex Salmond doesn't seem to understand that devolution has the support of a large majority of Scots and is a completely different concept to separation, which Scotland has always rejected."