Britain’s armed forces would destroy Iranian missiles fired at London, Sir Keir Starmer has said.
Downing Street said the country has defensive systems to protect the capital against such an attack if Tehran attempted to carry one out.
Fears were sparked Iran could strike London after the Tehran regime launched two missiles in a failed attempt to attack the Diego Garcia joint UK-US military base at a distance of some 2,500 miles.
Responding to the development, the Prime Minister’s official spokesman said: “To be clear and to reassure the people, we have got the military capability we need in the UK to keep people safe from any kind of attacks, whether it’s on our soil or from abroad.
“We have got a layered approach and missile defence provided by Royal Navy, British Army and RAF assets,” he added stressing co-operation with Nato on this system.
Amid the claims Tehran could now hit London, Sir Keir said: “There’s no assessment that we’re being targeted in that way at all.
“But of course, it’s my job to ensure that British interests, British lives are always uppermost in my mind.”
Earlier, a former Nato chief said the threat of an attempted Iranian missile strike on London “has to be taken seriously”.
General Sir Richard Shirreff, who was Nato Deputy Supreme Allied Commander Europe, stressed that the risk of such an attack was “low but serious” as US bombers are using RAF bases to target Iran.
On the threat to London, Sir Richard told Times Radio: “The risks are low but nevertheless they are serious.”
He added: “If any country has a missile capable of travelling the sort of distances we are talking about with the sort of intent that Iran definitely has if we are supporting the United States by the use of bases then it’s a risk that has to be taken seriously.
“But the chances of it getting here are pretty remote given the Nato ballistic missile defences that exists between us and Iran, although the UK’s own capabilities frankly are pretty limited.”
His comments came after the Institute for the Study of War, a leading US military think tank, published a map showing London now theoretically in range of Iranian missiles.
Israel seized on the Diego Garcia incident to argue that Iran could now hit European cities.
“The Iranian terrorist regime poses a global threat,” the Israeli Defence Forces said.
“Now, with missiles that can reach London, Paris or Berlin.”
Housing minister Matthew Pennycook, on the morning media round for the Government, stressed that London and other parts of the UK would be protected by recently improved defensive systems.
“We have the means necessary to defend this country from attacks from our own soil or from abroad,” he told told Sky News.
“We have invested as a Government in air and missile defence following the recommendations that came out of the Strategic Defence Review.”
Mr Pennycook, MP for Greenwich and Woolwich, also emphasised that Israel is an “active participant” in the conflict so its statement on London should be viewed in that context.
Sir Keir was on Monday convening an emergency Cobra meeting after a call with Donald Trump to discuss reopening the Strait of Hormuz, through which a fifth of the world’s oil supplies are transported.
In a conversation on Sunday night, the Prime Minister and the US president agreed reopening the strait was “essential” to stabilise a global energy market that had seen oil prices rocket since Trump launched his Iran war.
The 20-minute call, described by sources as “constructive”, followed a week in which Trump had heavily criticised Sir Keir’s response to the crisis amid the president’s demand for other nations to send warships to open the strait.
Other nations have so far resisted his demand, with the UK thought to be unlikely to send Royal Navy warships because of the high level of risk in the strait and an unwillingness to be drawn into the wider war.
But while the strait remains effectively closed to most shipping, the impact on the global energy market and the global economy is set to continue.
Facing the threat of higher inflation and concerns about disruption to fuel supplies, Sir Keir was due to hold crisis talks at the emergency Whitehall meeting as petrol prices and mortgage rates have risen, with warnings that energy bills could go up by more than £300.
Chancellor Rachel Reeves, Foreign Secretary Yvette Cooper and Energy Secretary Ed Miliband were expected to join the meeting, as well as the governor of the Bank of England, Andrew Bailey.
The meeting was expected to focus on the economic impact of the crisis, energy security and the resilience of industry and supply chains alongside the international response.
On Sunday, the chief executive of Centrica, which owns British Gas, said global oil supplies are already down 20 per cent because of the conflict and warned price rises were “inescapable”.
But the Government is keen to play down the prospect of fuel rationing and discourage people from panic-buying petrol.
