THERESA May has said Western allies must continue to "deter and counter" Russia's efforts to undermine their interests and values.

The Prime Minister told MPs that she welcomed the meeting of Donald Trump, the US President, and Vladimir Putin, his Russian counterpart, in Helsinki.

Making a statement to the Commons on last week's Nato summit, she said: "But as I agreed with President Trump in our discussions last week, we must engage from a position of unity and strength.

"This means being clear and unwavering about where Russia needs to change its behaviour, and for as long as Russia persists in its efforts to undermine our interests and values, we must continue to deter and counter them."

Mrs May, in response to questions from Jeremy Corbyn, said Mr Trump had “made a difference” at the Nato summit.

"We share his view that we want to see allies all stepping up to meet the commitment they gave at the summit in Wales in 2014 to spend two per cent of their GDP on defence and 20 per cent of that on equipment.

"It's something we meet and a limited number of other members of Nato meet, including the USA.

"His making this point about burden-sharing has made a difference; just in the last year we've seen an extra $41 billion added to defence budgets across the Nato allies, and there was a real sense at this summit following the discussion that he initiated that we would see people not just stepping up in terms of going to meet their two per cent but seeing that there was an increased urgency in doing this."

Earlier, the Labour leader argued that last week's Nato summit was an opportunity for the alliance to reset its approach to challenges facing the world, adding: "Once again, another global gathering has been dominated by the erratic statements of President Trump."

He went on: "Under no circumstances can our policies be outsourced to the whims of Washington."

Mr Corbyn also quipped if Mrs May would condemn Mr Trump's "preferred choice as her successor" as UK Prime Minister in a nod to remarks made by the President about Boris Johnson, the former Foreign Secretary.

He added that Mrs May's "chaotic" approach to Brexit talks "risks future security and defensive co-operation" with the EU.

But, noting how Nato had been the backbone of Europe’s security since its inception, the PM suggested it sounded as if the Labour leader had changed his mind on the alliance.

“Because it was not that long ago that he said about Nato: ‘I’d rather we weren’t in it,’ and: ‘Why don’t we turn it around and close down Nato?” Well, we are not going to close down Nato,” declared Mrs May, adding: “The United Kingdom will continue to contribute to Nato as the backbone of European security and wider security around the world.”

Later, Ian Blackford for the SNP accused Mr Trump of "embarrassing" behaviour at the Nato summit, telling MPs: "Shambolic scenes from a US President who takes a childish approach to foreign and security policy rather than work with allies to tackle common security threats."