The UK Government today launched an unprecedented attack on the US, its closest ally, over John Kerry's condemnation of the Israeli regime as the 'most right-wing in history'.

In a highly critical speech on foreign policy yesterday the US Secretary of State criticised Irsaeli PM Benjamin Netanyahu for undermining the two-state solution with his settlement policy in the West Bank.

Britain backed a UN Security Council resolution calling for an end to Israel's construction of settlements in the hotly-disputed region but Mr Kerry went further with his strongly-worded personal attack on Mr Netanyahu and his government.

A spokesman for Prime Minister Theresa May said it was inappropriate of Mr Kerry, America's top diplomat, to attack the make-up of the democratically-elected Israeli government – a key ally of both the US and Britain.

A spokesman for Prime Minister Theresa May, pictured left, said it was inappropriate of US Secretary of State John Kerry, right, to attack the make-up of the democratically-elected Israeli government – a key ally of both the US and Britain

Downing Street also rebuked Mr Kerry for focusing on the single issue of Israeli settlements and not the whole conflict.

Intervening in the increasingly hostile international dispute today, a spokesman for the British Prime Minister said: 'We do not... believe that the way to negotiate peace is by focusing on only one issue, in this case the construction of settlements, when clearly the conflict between the Israelis and Palestinians is so deeply complex.

'And we do not believe that it is appropriate to attack the composition of the democratically-elected government of an ally.'

'The Government believes that negotiations will only succeed when they are conducted between the two parties, supported by the international community.'

It echoes Mr Netanyahu's riposte yesterday when he accused the US Secretary of State of being skewed against Israel' and talking 'obsessively' about settlements.

President-elect Donald Trump also weighed in to defend the Israeli government.

In his speech yesterday Mr Kerry, who is leaving his post next month along with President Barack Obama, said the only way to achieve peace between Israelis and Palestinians in the Middle East is through a two-state solution to the disputed West Bank.

'That future is now in jeopardy,' the US Secretary of State said.

In a highly critical speech on foreign policy yesterday the US Secretary of State John Kerry, pictured, criticised Irsaeli PM Benjamin Netanyahu for undermining the two-state solution with his settlement policy in the West Bank

Israeli Prime Minister Benjamin Netanyahu, pictured accused the US Secretary of State of being skewed against Israel' and talking 'obsessively' about settlements

President-elect Donald Trump weighed in to the dispute to defend the Israeli government

He added: 'The Israeli prime minister publicly supports a two-state solution, but his current coalition is the most right-wing in Israeli history with an agenda driven by the most extreme elements.

'The result is that policies of this government, which the prime minister himself just described as more committed to settlements than any Israel's history, are leading in the opposite direction. They are leading towards one state.'

Downing Street insisted it still opposed Israel's 'illegal' construction of settlements in the West Bank and said its criticism was expressing unease at his comments attacking the make-up of the Israeli government.

A spokesman said: 'The British Government continues to believe that the only way to a lasting peace in the Middle East is through a two-state solution.

'We continue to believe that the construction of settlements in the Occupied Palestinian Territories is illegal, which is why we supported UN Security Council Resolution 2334 last week.

'But we are also clear that the settlements are far from the only problem in this conflict. In particular, the people of Israel deserve to live free from the threat of terrorism, with which they have had to cope for too long.'

The US State Department hit straight back, pointing out that nine other major nations had backed Mr Kerry's condemnation of Mr Netanyahu.

A spokesperson said: 'We are grateful for the strongly supportive statements in response to Secretary Kerry's speech from across the world, including Germany, France, Canada, Jordan, Egypt, Turkey, Saudi Arabia, Qatar, the United Arab Emirates and others.

'We are surprised by the UK Prime Minister's office statement given that Secretary Kerry's remarks—which covered the full range of threats to a two state solution, including terrorism, violence, incitement and settlements—were in-line with the UK's own longstanding policy and its vote at the United Nations last week.'

Israeli Prime Minister Benjamin Netanyahu derided U.S. Secretary of State John Kerry's speech yesterday on Mideast peace process as 'unbalanced' and warned him against additional provocation in the 'waning days' of the Obama administration

Benjamin Netanyahu called the Kerry speech 'unbalanced' and mocked President Obama by posting a picture to his Facebook page of him as a presidential candidate in 2008 visiting the Western Wall and noted that the US is now calling it 'occupied Palestinian territory. 'Seriously?' he wrote

Mr Kerry's speech sparked a major diplomatic war of words between the US and Israeli governments.

Mr Netanyahu called the speech 'unbalanced' and said that 'Israelis do not need to be lectured on the importance of peace'.

He posted a picture to his Facebook page of Mr Obama visiting the Western Wall in 2008 when he was a presidential candidate and noted that the US is now calling it 'occupied Palestinian territory. 'Seriously?' he wrote.

Mr Netanyahu also penned a note of thanks to Mr Trump for his 'clear-cut support' for Israel.

The social media post came after Trump tweeted his own message of support for Israel.

Mr Trump and the outgoing Obama administration are now entirely at odds over Israel, with the president-elect accusing the lame-duck White House of 'disdain and neglect' for the country.

Donald Trump and the outgoing Obama administration are now entirely at odds over Israel, with the president-elect accusing the lame-duck White House of 'disdain and neglect' for the country

The Republican President-elect took to Twitter to say Israel had been treated 'very, very unfairly' by the Obama administration and maintained that countries that are 'horrible places' never get reprimanded.

He refused to directly answer a question about whether Israel should stop building settlements, saying he is 'very, very strong on Israel'.

Mr Trump said Israel is 'up for 20 reprimands' at the United Nations, whereas nations that are 'horrible places, that treat people horribly, haven't even been reprimanded.'

His comments follow the United Nations' condemnation of the construction of Israeli settlements in the West Bank and east Jerusalem.