In a week where the Trident issue will be getting renewed attention it is important to nail some of the wild assertions and fallacies about Scottish public opinion on the subject.

Two recent serious tests of public opinion have been carried out by polling organisations. One was commissioned by Lord Ashcroft, the Tory peer, and the other by the House of Commons Select Committee on Public Administration. Both give the lie to the claim that the Scots are overwhelmingly opposed to continuing with Trident.

The Lord Ashcroft survey was specifically done in Scotland (and partially covered in this newspaper) and put to people that the Trident system was coming to the end of its useful life and it would have to be scrapped or replaced.

Only one-third (34%) said the UK should give up nuclear weapons completely. More than half thought that Trident should be replaced either by an equally powerful system (20%) or a cheaper, less powerful system (31%).

The Public Administrative survey asked a UK audience: "If the UK Government decided there is no cheaper alternative for an effective nuclear weapons system, and you had to choose between keeping the current nuclear weapons system or giving up nuclear weapons altogether, which of the following statements would come closest to your view?"

The answers? The UK should order four new submarines to maintain its nuclear weapons system – 57%; the UK should give up nuclear weapons altogether – 27%; don't know – 17%. A decisive majority.

In Scotland, 49% opted for the "order new submarines" statement, 43% for "abandon nuclear weapons", and 8% were don't knows.

It should be noted that 49% is four percentage points more than the SNP polled in the 2010 General Election.

If we are to continue having a rational discussion in the run up to the referendum vote these facts must be a better guide than baseless assertions on the state of Scottish public opinion.

George Robertson,

Former Secretary of State for Defence and Secretary General of Nato,

House of Lords, London.

Champions of Trident often describe the protection it apparently affords us all in terms of an "umbrella" but I prefer the Dickensian word "gamp"; it stands for Generally Assured Mutual Pulverisation.

Dr Hamish Maclaren,

1 Grays Loan,

Thornhill,

Stirling.