Sir Menzies Campbell, a member of the Parliament Intelligence and Security Committee, writes on the weaknesses of the SNP's plans for new security services in the event of independence.
Sir Menzies' intervention comes after former MI6 chief Sir John Scarlett warned that independence would leave Scotland less protected from threats:
"It is a well established principle that the primary responsibility of any government is to protect the lives and liberty of its citizens. The importance of these issues was highlighted as MPs returned to Westminster this week.
"From the SNP in the Commons there was no contribution to the debate about how best to balance the competing principles of security and freedom. Some argue that the responsibility to protect is more important than the currency a country uses or its membership of international organisations like the European Union. All of which makes it all the more curious that in the debate about Scotland's future there has hardly been a moment's discussion about how best to protect Scotland's security in the event of independence.
"In the modern world of cyber terrorism and suicide bombings, fulfilling this responsibility to protect requires a sophisticated and professional a response. No part of this response is more important than intelligence gathering. In the United Kingdom this is provided by MI5, MI6 and GCHQ. These are among the best in the world. They are active on our behalf twenty four hours a day, seven days a week. Their personal lives are restricted by the nature of their work and their lives are often at risk as are those of their families.
"The United Kingdom spends approximately £2 billion per annum on its three intelligence services. When challenged about the financial provision a Scottish Government might make for intelligence services the SNP says that it would spend £200 million a year, one tenth of the United Kingdom total. This appears superficially attractive but is far from reality. It does not take account of the capital investment required to provide the infrastructure necessary to establish three equivalent capabilities. Nor does it recognise the start-up costs necessary for recruitment, training or secure accommodation. Half-baked does not describe it!
"Challenges to the SNP policy on intelligence are met with a bland assertion that the threats to an independent Scotland would be less than to the United Kingdom, a proposition for which no evidence is offered and which is seriously undermined by a previous attempt at Glasgow airport to kill and maim hundreds of passengers in the terminal.
"Nor does it take account of the principle that terrorists will always seek the softest and most unsuspecting targets. No country is exempt from terrorist attacks, whether external or internal, as was found in Norway in the needless slaughter of so many young men and women. It follows that Scotland, with an open border with the rest of the UK for which the Yes campaign argues, would provide an attractive means of easy access to targets outside Scotland but within these islands.
"Is all of this fanciful? Consider this. At any one time, MI5 are conducting several hundred operations in their efforts to prevent acts of terrorism. Consider also the public knowledge that there are a number of jihadists who are citizens of the United Kingdom now well trained in terrorism, returning to the UK with the potential to put to use the skills they have acquired and who have the motive to use these skills.
"It is of course true that if the United Kingdom was satisfied that an independent Scotland had established credible intelligence services there would be scope for cooperation, just as there is between the UK and other foreign Governments. But such arrangements would depend on satisfaction that Scottish fledgling intelligence services were both competent and could be trusted with sensitive information. Such necessary professionalism and trustworthiness could only be built up over time and would be a necessary pre-requisite of serious cooperation.
"But even that cooperation would be qualitatively different from the current arrangements for Scotland's security. Scotland would no longer be a part of the UK's intelligence infrastructure. In practical terms, in the present level of strategic and operational integration in Britain, Scotland plays a key role. This would come to an end. Remember too that intelligence gathering focuses not only on the safety of citizens but on organised crime and cyber threats. Scotland, in the process of establishing its own security services, would be an inviting target for economic espionage and cyber attack.
"Policing, justice and our legal system are all properly devolved to Edinburgh but national security is reserved to Westminster and with good reason. The whole of the United Kingdom - Scotland included - sees significant benefit from having UK-wide security services, not least through the long standing and productive relationships established by MI5, MI6 and GCHQ with similar agencies abroad. These relationships arise out of partnerships which have taken a long time to build up and are not readily entered into and must be earned.
"It is very rarely that one source of intelligence is conclusive. Often conclusions can only be reached by building up a pattern of behaviour which relies on multiple sources. The wider the range of cooperation with countries prepared to share intelligence the better the chance of establishing a pattern from which valid conclusions can be made.
"I very much doubt there are many whose votes on 18th September will be affected by close analysis of intelligence and security issues. But there can be no doubt that what we have at the moment through the United Kingdom is materially better than anything an independent Scotland is likely to provide for a very long time, if ever."