A GENERATION ago it would have been unthinkable for the fiercely anti-nuclear Scottish National Party to propose that an independent Scotland should join Nato.

Yet, the party's autumn conference will consider a motion that Scotland should remove nuclear weapons but join the North Atlantic Treaty Organisation, whose ultimate deterrent in nuclear weaponry.

Since it is to be put forward by Angus Robertson, the SNP's Westminster leader and defence spokesman, this can be taken as the preferred policy option of the leadership. If it is agreed, it will breach a shibboleth for many of the party's most faithful foot soldiers. For 30 years the SNP's stance has been anti-Nato because the party is opposed to nuclear weapons and, as Nato is a nuclear alliance, an independent Scotland would not apply for membership. For many grassroots members and activists, especially on the left of the party, this was a point of principle and the reason for joining the SNP rather than Labour.

Expelling Trident from Faslane and Coulport but remaining a member of Nato is a compromise solution that would leave the SNP vulnerable to charges of hypocrisy. While the party can claim it remains committed to the earliest possible withdrawal of Trident from Scotland, some experts say that removal could take up to 20 years.

At the autumn conference, two years away from the referendum on independence, Alex Salmond and his key lieutenants will be looking beyond their membership to the wider electorate. Seeking Nato membership is a bold move on the part of Mr Salmond, in keeping with his reputation as a politician who likes to take risks. The aim will be to convince waverers that Scotland's security will be guaranteed under independence.

But there are practical as well as moral questions to answer. Nato's latest Strategic Concept document asserts the supreme guarantee of security is nuclear deterrence. The SNP gives the example of Norway and Denmark as countries which are also opposed to nuclear weapons but committed Nato members. However, they have never had nuclear weapons. An independent Scotland that had just closed Nato bases might fairly be regarded as having sabotaged its claim to be strategically essential while attempting to hitch a free ride. Nevertheless, if Nato's ultimate goal of creating the conditions for a world without nuclear weapons is to be taken seriously, as it must in any country which values peace and human rights, individual member states must be able to opt out of enforced hosting of nuclear weaponry.

The SNP is aware that its policies must provide answers to the concerns of the people of Scotland if it is to win the referendum. Rightly, defence is a major consideration. Altering strategy to take account of the changing world situation is entirely reasonable but changing tack to gain political momentum risks been seen as opportunistic. On this thorny question motive is as vital as outcome.