No 10: raising limit on UK's nuclear warhead stockpile not a Treaty breach

It insists vigilance is needed as some states are “now significantly increasing and diversifying their nuclear arsenals”.

While the review says the UK will not use, or threaten to use, nuclear weapons against any non-nuclear weapon state, party to the 1968 Non-Proliferation Treaty, it makes clear this assurance “does not apply to any state in material breach of those non-proliferation obligations”.

Also, it stresses Britain will “review this assurance” if the future threat from biological and chemical weapons or cyber technology “makes it necessary” to do so.

The Scottish Government denounced as “utterly unacceptable” the UK Government’s decision to increase the ceiling on the nuclear warhead stockpile in Scotland.

Humza Yousaf, its Justice Secretary, described nuclear weapons as “morally, strategically and economically wrong” and declared: “Our opposition to Trident remains unequivocal.”

As the UK Government’s political opponents and anti-nuclear campaigners claimed increasing the limit of stored warheads would break Britain’s treaty obligations, No 10 denied this.

Boris Johnson’s spokesman said: “The Nuclear Non-Proliferation Treaty doesn’t require us to reduce the number of warheads. All of our actions are consistent with our Nuclear Non-Proliferation Treaty obligations.”

He explained the Government believed the best way to protect the UK and its Nato allies was to ensure the country continued to have a credible independent nuclear deterrent.

“The 260 figure is a ceiling, not a target,” declared the spokesman. “We will continue to keep this under review in the light of the international security environment and make adjustments as appropriate.”

In the Commons, pointing out how Britain’s entire nuclear submarine fleet was based on the Clyde, the Prime Minister told MPs the first outcome of the review involved “taking forward the renewal of our nuclear deterrent”.

He clashed with Sir Keir Starmer after the Labour leader insisted his party’s “support for nuclear deterrence is non-negotiable,” noting, however, the review “broke the goal of successive prime ministers and cross-party efforts to reduce our nuclear stockpile”.

Mr Johnson took Sir Keir to task, saying the Opposition was “all over the place” on Trident. “The last time the House voted on protecting our nuclear defences, the Shadow Foreign Secretary[Lisa Nandy] voted against it and so did the current Labour deputy leader[Angela Rayner].”

Scottish Labour still opposes the renewal of Trident.

In the Commons, Ian Blackford for the SNP also claimed the review, which “disgracefully endorses the attainment of 80 more of these weapons of mass destruction,” was a breach of Treaty obligations.

The PM insisted the Government would continue to “invest massively in projects that will bring benefit to the whole of the UK, including Scotland”.

He told the Nationalist leader there was “no threat to the Black Watch, which he and his colleagues sometimes like to raise in order to alarm people,” and warned the only thing endangering defence investments was the “reckless referendum” proposed by the SNP “at the most inapposite time possible for this country”.

The review describes a “deteriorating security environment” in the world with the proliferation of chemical and nuclear weapons, advanced conventional weapons and “novel military technologies” increasing “the risk and intensity of conflict”.

It warns it is “likely” a terrorist group will launch a successful chemical, biological, radiological or nuclear attack by 2030.

The document sets out the UK’s aim to be a “science and tech superpower” by 2030 with the ability to “monitor, protect and defend our interests” in space and ensuring cutting-edge defensive and offensive cyber capabilities.

It states tackling climate change is the Government’s “number one international priority” in 2021 and beyond.