Britain's Defence Secretary Gavin Williamson has accused Russia of spying on its critical infrastructure as part of possible plans to create “total chaos” in the country that could “cause thousands and thousands of deaths”.

In unusually alarmist words from a senior minister Williamson told the Daily Telegraph that, in its research on the UK power supply connections with Europe, Moscow appeared intent on sowing “panic” and hurting Britain.

“What they are looking at doing is they are going to be thinking 'how can we just cause so much pain to Britain?'” he said in comments published on Thursday night.

“Damage its economy, rip its infrastructure apart, actually cause thousands and thousands and thousands of deaths, but actually have an element of creating total chaos within the country.”

Williamson, who only became defence chief in November after predecessor Michael Fallon resigned over allegations of misconduct, gave the interview at the outset of a new five-month defence review.

He is reportedly pressuring finance minister Philip Hammond to allocate more money to defence and scrap further cuts to Britain's strained armed forces.

In the interview, the minister said Russia acts in a way “that any other nation would see as completely unacceptable”.

“Why would they keep photographing and looking at power stations, why are they looking at the interconnectors that bring so much electricity and so much energy into our country,” he questioned in the paper.

“They are looking at these things because they are saying these are the ways that we can hurt Britain.”

Earlier this week Fallon joined calls from the head of the army for more British military spending, amid warnings the country may struggle to match Russian battlefield capabilities.

Meanwhile, the head of the National Cyber Security Centre said the country will likely face a major cyber-attack within two years.

Ciaran Martin told The Guardian it was inevitable a hostile actor would launch an online attack aimed at crippling Britain's critical infrastructure, such as energy supplies, and it was lucky not to have fallen victim to such a strike already.

Williamson, who is tipped as a possible future ruling Conservative party leader, described his scenario planning as “the real threat that I believe the country is facing at the moment.”

A spokesman for the Ministry of Defence said it had nothing further to add to his remarks.

The Russian Embassy in London could not be reached for comment Thursday.