HUNDREDS of British troops are to be sent to the border with Russia as David Cameron battles to assure allies and enemies alike that Brexit will not damage the UK’s defences.

The Prime Minister will today tell other Nato countries that they have Britain’s “steadfast” support, including boots on the ground.

At his final Nato summit in Warsaw, Mr Cameron will announce a 500-strong battalion will be sent to Estonia.

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A further company of 150 troops will be stationed in Poland “on an enduring basis”.

The UK will also take over the leadership of the nuclear alliance’s rapid reaction force from January, with 3,000 troops on standby to move in as little as five days.

But Mr Cameron is likely to face questions from other world leaders about what leaving the EU will mean, including for Scottish independence and the future of the UK’s nuclear deterrent.

MPs are expected to vote on replacing Trident within the next two weeks.

A Conservative source said that they would be asked to back a like-for-like replacement for the ageing system on the Clyde .

MPs “will vote on four boats... four boats was in our manifesto, so we will be fulfilling a manifesto commitment,” he said.

A Whitehall source added that Mr Cameron was “clear” that the UK “needs to keep” its nuclear weapons.

On the Nato meeting, the source added: “This will be a summit where you will see Britain assert itself as one of the most crucial elements in the Nato alliance.

“Not only are we going to be steadfast in our support of Nato, but we are prepared to back that up with boots on the ground.”

Mr Cameron will also use the meeting to underline the importance of the UK meeting Nato’s spending target of two per cent.

"There can be no backsliding on this issue," a Government source said.

"The PM is very clear that the two per cent commitment is absolutely crucial to Nato going forward."

But his interventions risk being seen as attempts to bind the hands of his successor as much as signals to others countries.

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There are increasing concerns about Russia, following the annexation of Crimea from Ukraine in 2014.

The use of extra UK troops is intended to underline Nato’s commitment to the collective defence of all of its members – including the Baltic States of Latvia, Lithuania and Estonia.

Like Ukraine all three have significant Russian-speaking minorities.

Nato Secretary General Jens Stoltenberg said that Russia had tripled its defence spending since 2000.

"This has really changed our security environment. Nato has to respond. When the world is changing, we have to change,” he said.

But SNP MPs said that the Kremlin believed Britain “doesn’t have a scooby” about how it wants to work with European neighbours to counter the Russian threat.

Brexit is one reason Russia believes the UK’s strength in the world has been “profoundly weakened”, the SNP’s Martin Docherty-Hughes said.

The West Dunbartonshire MP voiced concerns about the lack of investigation by the Commons Defence Committee into the consequences of the UK leaving the EU.

The Conservative chairman of the committee, Julian Lewis, said he “utterly” disagreed with the criticism and that the issue was high on the agenda of future work.

But Mr Docherty-Hughes told MPs: “It’s now clear that the Russian Federation views the United Kingdom’s global strength as profoundly weakened, not only by the issues raised by the committee in its report but by Brexit.”

Shadow defence secretary Clive Lewis said it was vital for the UK to ensure that Brexit did not “undermine” Nato’s political cohesion.

Speaking ahead of the meeting in Warsaw, Mr Cameron said: "This summit is a chance for us to reiterate our strong support for Ukraine and our other Eastern allies to deter Russian aggression.

"Actions speak louder than words and the UK is proud to be taking the lead role, deploying troops across Eastern Europe. It is yet another example of the UK leading in Nato."

Yesterday the Foreign Secretary Philip Hammond defended the government's lack of contingency planning for the Brexit vote.

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He told MPs any work would have been denounced by the Leave camp as “unwarranted intervention”

Meanwhile, banking giant JP Morgan has reiterated his warning that the company could move thousands of jobs out of the UK in the wake of the decision to leave the EU.