Ministers need to be honest with the British public about the immediate threat posed by Russia which could soon lead to lives being lost, a former national security adviser has said.

Peter Ricketts, who advised David Cameron when he was prime minister, became the latest figure to warn about the scale of the threat posed by "hybrid attacks" from Vladimir Putin's forces.

The peer, who is the former top civil servant in the Foreign Office, said banking systems, energy or water supplies could be targeted by Kremlin cyber-assaults. He called for further investment in resilience for key sectors. It comes in a week where the heads of and the British army have warned about the danger posed by Moscow.

Lord Ricketts also dismissed Andy Burnham's claim he wanted to be a "bridge" between the US and Ukraine.

Relations between Washington and Kyiv deteriorated sharply this week after Donald Trump waived a number of economic sanctions on Russia and suggested Ukraine needed a new leader.

Speaking to BBC Radio 4's Today programme, Ricketts said: "I think they've really got to start a conversation with the British people about what may be coming, because not only is Putin trying to break morale in Ukraine, he's also trying to undermine morale in European countries." In response to a question over the impact of disruption by Russia, he added: "I'm not saying there's going to be industrial war with tanks rolling across the north German plain.

"But these hybrid attacks are getting more reckless, more dangerous. One day, people are going to land up being killed somewhere, and so we are going to have to look at responding in that sense and finding the money to do it."

Speaking about Burnham's comments at prime minister's questions this week saying he wanted to be a bridge between Washington and Kyiv, Ricketts said: "I don't really go on this bridge business. I mean, I don't think in Trump's current mood there's any influence that Britain can have in the short term." Ricketts's comments join those by the director general of MI5, Sir Ken McCallum, and the chief of the general staff, Gen Sir Roly Walker, in the last few days about Russia.

On Tuesday, McCallum said MI5 was devoting more resources to combating threats from hostile states than it did during the cold war and described Russia as the "number one aggressor".

And on Friday, Walker told 700 troops at Catterick garrison in North Yorkshire that politicians would soon need to have a "frank conversation" about the "sacrifices" that would be needed to prioritise defence and security.

Walker, a former special forces commander, said soldiers would probably need to fight in a war given the "extreme jeopardy in the world at the moment".

The warnings come after a difficult week for Kyiv, with the US appearing to withdraw support.

Trump said the decision to pause sanctions was in the US "national interest", despite previouslyg them into law in September.

Last week, he lifted restrictions on Russian diesel amid spiralling fuel prices in the US ahead of the midterm elections.

He also suggested Ukraine needed a new president. Volodymyr Zelenskyy hit back this week during an EU summit, saying it was nice to be among "real leaders".

There are also concerns that the US has withdrawn intelligence sharing with Ukraine, leaving towns and cities across the country vulnerable to attack.

Ricketts said the government should spend more money on protections for key infrastructure in Britain, including energy, transport, air traffic control and defence.

He said: "They all need better protection, and that's an argument that needs to be had with the British people because we need to find the money to do it."