BORIS Johnson has been “hobbled” in his role as Foreign Secretary and should have a greater say over the UK’s strategy on Brexit, according to the Chairman of the Commons Foreign Affairs Committee.

Tom Tugendhat will use a keynote speech tomorrow to call for a "revolution" at the heart of the UK Government.

Such a shake-up would see the Foreign Secretary gain strategic control over diplomacy, intelligence, defence, development aid, international trade and leaving the EU, he will argue.

Mr Tugendhat, a Kent MP, will tell the Royal United Services Institute for Defence and Security Studies think-tank: "Successive foreign secretaries - including the current one - have been hobbled. They've had the title but they haven't had the power."

He adds the Foreign Office "has lost control of key aspects of overseas influence" like trade and development.

Mr Tugendhat, a former Army officer often tipped as a future Tory leader, will claim the great office of state in Whitehall has been forced into a tug-of-war with the Cabinet Office over anything that involves national security and the EU.

He will add in his speech: "This has created silos in our foreign policy reducing our ability to balance across areas of influence.

"The success or failure of our foreign policy is now more important to the future health and prosperity of our nation than it has been at any time since the end of the Second World War.

"We need to make the Foreign Office the strategic engine of our foreign policy again."

Meanwhile, Mr Johnson has stressed the need for the UK to come "fully out" of the EU customs union if the UK is to be a global trading nation.

The Secretary of State's latest intervention comes after influential backbench Tory Brexiteer Jacob Rees-Mogg called on Theresa May at the weekend to take a tougher line with Brussels in the negotiations.

Mr Johnson said that his recent trip to Latin America - during which he urged the Prime Minister to "get on with it" and take Britain out of the customs union "as fast as is reasonably possible" - made it clear that potential trading partners wanted the UK out of the EU tariffs arrangement.

"Now is our moment not to be less European - we can do a great free trade deal with the EU that will benefit both sides - but to be truly global again," he declared.