Energy assets must be given critical national infrastructure status as a “priority” amid reports of Russian vessels near pipelines in Scotland, the Conservatives have said.

A letter sent by the party to the Labour UK Government called for urgent action to protect offshore pipelines.

The letter is signed by shadow Scottish secretary Harriet Cross, shadow defence secretary James Cartlidge and shadow energy security secretary Andrew Bowie.

Ms Cross said the Government must take “stronger action to deter hostile states”.

She said: “Scotland is on the front line of the growing threats from states such as Russia and China.

“Energy security is national security and reports of vessels from these hostile nations operating close to vital pipelines off our coast should set alarm bells ringing for Labour ministers.

“These pipelines bring the gas that millions of households and businesses depend on. Any disruption would have catastrophic and potentially long-lasting consequences.

“Labour ministers must take stronger action to deter hostile states and ensure that Scotland’s offshore energy assets receive critical national infrastructure status.”

The three MPs have called on the Labour Government to strengthen protections for offshore infrastructure, deter hostile states, assess alternative gas supplies, and ensure all relevant offshore energy assets receive critical national infrastructure status.

The Tories have also been critical about the lack of defence funding announced in the Budget last week.

Mr Cartlidge said: “The sighting of Russian and Chinese vessels in British waters underlines why we cannot afford to be complacent about the threats to the realm.

“Yet at last week’s Budget, Labour again failed to commit to spending 3% of GDP on defence. Kicking the can down the road is leaving our Armed Forces without the certainty they need.”

Mr Bowie claimed Labour and the SNP “continue to undermine the very industry that keeps the lights on for businesses and families”.

He said: “The ongoing refusal to back Rosebank and the ban on new oil and gas licences is putting our energy security, thousands of skilled jobs and billions of pounds of investment at risk.

“Scotland’s energy infrastructure must be given the protection it deserves. That means recognising offshore energy assets as critical national infrastructure and backing our domestic oil and gas industry.”

A UK Government spokesperson said: “National security is our top priority.

“We’re delivering nearly £300 billion for defence over the next four years, the biggest sustained increase since the Cold War, and last month we announced plans for new security and resilience laws which would see subsea pipeline and cable saboteurs facing jail and unlimited fines.

“We continue to work closely with the sector to protect vital offshore and subsea energy infrastructure against a range of threats.”

Scottish energy minister Stephen Gethins, who has been sanctioned by Russia for his activities in opposing Vladimir Putin’s actions, said: “We know that there is an increased threat level, including to critical energy and other infrastructure, and the UK Government must ensure it is doing all it can to defend us from those threats.

“It was only a few months ago that the now Chancellor resigned (as defence secretary) to make that point, and yet the new Defence Secretary is not able to explain how or when the UK Government will actually make the necessary investments in defence.

“That is because the UK has spent hundreds of billions on weapons of mass destruction, while neglecting investment that would protect us from the threats we actually face.

“The UK chose to scrap its entire maritime patrol fleet, leaving Scotland’s vast coastline dangerously exposed, and has chosen not to base a single offshore patrol vessel, frigate or destroyer in Scotland – requiring vessels to be dispatched from the south coast of England.

“An independent Scotland would not make those choices or leave those gaps. Our priority would be the adequate defence of our strategically important waters and our shores, as well as acting as a reliable, responsible global partner and contributing to our collective defence as an independent member of the European Union and Nato, where the majority of members do not host nuclear weapons.

“We would also strengthen defence co-operation with European partners, including through the EU’s Security Action for Europe programme, which even Canada has joined while the UK remains limited to third-party status only.”