Sir Keir Starmer has appointed Sir Tony Blair’s former chief of staff Jonathan Powell as National Security Adviser.

The veteran diplomat, who served for 17 years in the Foreign Office, will take over from Sir Tim Barrow in the role based in 10 Downing Street.

The Prime Minister said his experience in helping to negotiate the Good Friday Agreement and working on “some of the world’s most complex conflicts” meant he was “uniquely qualified” to advise the Government on global challenges.

Mr Powell was also involved in talks over the Chagos Islands sovereignty dispute, which earlier this year saw Britain hand the territory over to Mauritius.

He will now be expected to play a key role in forging links with Donald Trump’s new US administration, as well as helping to shape the UK’s response to conflicts in Ukraine and the Middle East.

“Jonathan has devoted his career to protecting the interests of the country, having served for 17 years as a diplomat in the Foreign Office and 10 years as chief of staff in No 10, and I am delighted to appoint him to this important role,” Sir Keir said.

“Together with his experience helping to negotiate the Belfast (Good Friday) Agreement and work on some of the world’s most complex conflicts, he is uniquely qualified to advise the Government on tackling the challenges ahead and engage with counterparts across the globe to protect and advance UK interests.

Thanking Sir Tim for his tenure during “some of the most challenging times in recent history”, the Prime Minister added: “I’ve no doubt he will continue to play a positive role on these issues in the future.”

There had been speculation under the previous Tory government that Sir Tim would move on to replace Dame Karen Pierce as Britain’s ambassador to the US, but she is now expected to remain in post.

“Having known Jonathan Powell for many years, I know he is very well qualified for this post. He will provide excellent support to the PM and the national security community,” Sir Tim said.

Mr Powell said: “I am honoured to have been appointed as the National Security Adviser to the Prime Minister. This is a hugely important role at a time where national security, international relations, and domestic policies are so interconnected.

“As the Prime Minister has set out, national security is at the heart of this country’s response to the many challenges we face and having an integrated response will be crucial to our success. I look forward to advising the Prime Minister and working closely with ministers and officials in this new role.”