Boris Johnson's efforts to halt the crisis in Ukraine risk being derailed by the partygate "timebomb", a former head of the Army has said.
General Lord Richard Dannatt said the country was "weakened" by the chaos swirling around the Prime Minister - and warned Mr Johnson's efforts to talk tough with Russia were being undermined.
The PM is considering doubling the number of troops stationed in Eastern Europe as he prepares to travel to the region amid mounting tensions over Ukraine.
He is also expected to speak to Russian President Vladimir Putin in the coming days, while Foreign Secretary Liz Truss and Defence Secretary Ben Wallace will meet their counterparts in Moscow.
Ms Truss said today that it was "highly likely" Russia would invade Ukraine as she warned President Putin the Ukrainians will "fight hard" and this could end up in a "quagmire".
But Lord Dannatt, who was Chief of the General Staff from 2006 to 2009, said that "flawed" leadership was undermining the UK's efforts.
He told TimesRadio: "We are in a mess domestically. I don't know which way partygate is going to roll. We've got to wait for Sue Gray, now compounded by the Met's intervention.
"I think Boris Johnson is in a very precarious position. And if, as the prime minister of this country at a time of an international crisis - and we are a powerful country but our leadership is flawed - then the West is weakened."
Asked it it was undermining the situation in Ukraine, he said: "Of course it is. We are weakened. He will travel to Moscow or wherever he's going in eastern Europe this week but everyone will know that he's a man with a time bomb sitting under him.
" Liz Truss is going to Moscow. Well, fine. She represents the British government, headed by Boris Johnson and his position is insecure.
"We've got to sort out the leadership of this country so that we can play our role as a permanent member of the UN Security Council, all the things that the UK stands for, in an unequivocal, clear way with a government of integrity and one that people can respect.
"We've got to get that sorted out. Either get behind Boris Johnson or get rid of him and let Rishi or someone take over."
It comes as Ms Truss said wealthy Russian oligarchs in Britain could be hit with tough new financial sanctions.
The Foreign Secretary suggested legislation for a new regime could come as early as this week.
“The most important thing is defending freedom and democracy and that is more important than immediate financial issues," she said.
“We cannot favour short term economic interests over the long term survival of freedom and democracy in Europe – that’s the tough decision that all of us have got to make.”
She later told the BBC : "There’s a real threat here for freedom and democracy in Europe. That’s more important than short-term economic pain."
Nato chief Jens Stoltenberg said it was a "good thing" the PM was willing to demonstrate that Nato was prepared to reach a diplomatic solution.
Ms Truss rejected claims that Russian links to the Conservative party and in British business would prevent the UK from punishing Russian aggression. US experts close to the White House have warned the wealth of kleptocrats invested in London – and their “close ties” to the Tory party – will thwart the UK’s pledges to act tough against Russia.
But Liberal Democrat MP Layla Moran told the Mirror: "How can we expect a Conservative party bankrolled by Russian money to get tough on dirty Russian money?
"The years of broken promises from the Conservatives on dealing with this have stunk of hypocrisy and self interest."
The Mirror revealed last year that almost a quarter of the ministers who attend cabinet have accepted donations from just three well-connected ex-Russians.
