Three former UK ambassadors to the Middle East will tomorrow join calls for Tony Blair to be removed from his role as Middle East peace envoy.

Signatories to an open letter, led by Mr Blair's former ambassador to Iran Sir Richard Dalton, describe his achievements in the region as ‘negligible’, criticise his money-making activities and accuse him of trying to ‘absolve himself’ of responsibility for the crisis in Iraq.

Other former diplomats to sign the letter are Oliver Miles, Britain’s ambassador to Libya when diplomatic relations were severed after the killing of WPC Yvonne Fletcher, and Christopher Long, ambassador to Egypt between 1992 and 1995.

Step down: Three former UK ambassadors to the Middle East will tomorrow join calls for Tony Blair to be removed as Middle East peace envoy

Tony Blair is under pressure to stand down as Middle East peace envoy over his continued support for military action in the region

Other signatories include former London mayor Ken Livingstone, former Conservative prisons minister Crispin Blunt, the human rights barrister Michael Mansfield QC and the former Liberal Democrat peer Lady Tonge, who resigned her party's whip in 2012 over anti-Israel remarks.

The letter has been organised by the makers of Respect MP George Galloway's film The Killing of Tony Blair. It has been timed for this week’s seventh anniversary of Mr Blair’s appointment as envoy on the Middle East to the ‘quartet’ of the UN, the EU, Russia and the US.

The letter is addressed to John Kerry, the US secretary of state; Sergei Lavrov, the Russian foreign minister; Ban Ki-moon, the UN secretary general; and Cathy Ashton, the EU's self-styled ‘foreign minister’.

It argues that Mr Blair’s 2003 invasion of Iraq is to blame for the rise of ‘fundamentalist terrorism in a land where none existed previously’ and he should be removed from his position.

The letter says: ‘We, like many, are appalled by Iraq's descent into a sectarian conflict that threatens its very existence as a nation, as well as the security of its neighbours. We are also dismayed, however, at Tony Blair's recent attempts to absolve himself of any responsibility for the current crisis by isolating it from the legacy of the Iraq war.’

It alleges that Mr Blair ‘misled the British people’ by suggesting Saddam Hussein had links to al-Qaeda.

‘In the wake of recent events it is a cruel irony for the people of Iraq that perhaps the invasion's most enduring legacy has been the rise of fundamentalist terrorism in a land where none existed previously. We believe that Mr Blair, as a vociferous advocate of the invasion, must accept a degree of responsibility for its consequences,’ it adds.

Criticising the former prime minister’s business interests, the letter alleges that his ‘conduct in his private pursuits also calls into question his suitability for the role’.

Mr Blair has faced criticism for a lack of transparency in the way he organises his personal finances. The letter accuses him of ‘blurring the lines between his public position as envoy and his private roles at Tony Blair Associates and the investment bank JPMorgan Chase.’

Mr Miles said: ‘Tony Blair is the wrong man in the wrong job. The wrong man because he is identified with the war in Iraq; criticism has concentrated on his misreading of intelligence and his lies, but equally important was his failure to plan for the peace, with the result we see today. The wrong job because patching up the Palestine economy sounds good but avoids the real issue, the repression and misery of the occupation; that is what the quartet should tackle. Seven years on it's time to blow the whistle.’

Former top diplomat Sir Richard Dalton is one of the signatories of the letter

Mr Blunt said: ‘It's time to end Tony Blair's personal calvary as quartet envoy following his disastrous statesmanship in office on the Middle East. His role as envoy was neutered politically almost as soon as it began, and is now a distraction from the increasingly desperate need for a comprehensive peace deal.’

The letter adds to growing calls for Mr Blair to stand down. Last week former foreign secretary Lord Owen criticised Mr Blair for his claims that the 2003 invasion was not a factor in the current unrest in Iraq.

‘Tony Blair should no longer be allowed to speak for the EU on the Middle East and someone else found for helping Palestine without his past record and crusading messianic fervour,’ he said.

A spokeswoman for Mr Blair said: ‘These are all people viscerally opposed to Tony Blair with absolutely no credibility in relation to him whatsoever.

‘Their attack is neither surprising nor newsworthy. They include the alliance of hard right and hard left views which he has fought against all his political life. Of course he completely disagrees with them over the Middle East. He believes passionately in the two State solution but also believes that can only be achieved by a negotiation with Israel.

‘The truth, and anybody who knows anything about the situation in respect of Palestine knows this, is that transformational change is impossible unless it goes hand in hand with a political process. There was hope that this could progress with the recent US led talks which were underpinned by a hugely ambitious economic plan spearheaded by Mr Blair.’

Of the criticism of Mr Blair's business interests, she added: ‘Mr Blair has done no work for JP Morgan in the Middle East – he is the chair of their International Advisory Council – where he provides advice on global political issues.’

Mr Blair’s allies also pointed out that Mr Miles had criticised the Chilcot inquiry into the Iraq war on the basis that two of its members ‘are Jewish’.