This Friday, 27 June, will mark the seven-year anniversary of Tony Blair's appointment as the Quartet representative to the Middle East. We, the undersigned, urge you to remove him with immediate effect as a result of his poor performance in the role, and his legacy in the region as a whole.

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.

In reality, the invasion and occupation of Iraq had been a disaster long before the recent gains made by the Islamic State of Iraq and Syria. The sectarian conflict responsible for much of the war's reprehensible human cost was caused in part by the occupying forces' division of the country's political system along sectarian lines.

In order to justify the invasion, Tony Blair misled the British people by claiming that Saddam Hussein had links to al-Qaida. 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.

The occupied Palestinian territories represent another tragic failure of western engagement in the Middle East.

It is our view that, after seven years, Mr Blair's achievements as envoy are negligible, even within his narrow mandate of promoting Palestinian economic development. Furthermore, the impression of activity created by his high-profile appointment has hindered genuine progress towards a lasting peace.

Seven years on there are still over 500 checkpoints and roadblocks in the West Bank. The Gaza Strip, severely damaged by Israel's 2009 bombing, remains in a humanitarian crisis, with 80% of its population reliant on foreign aid for survival. Israel continues to build settlements that are illegal under international law. According to the Palestinian Authority's former chief negotiator, Nabil Shaath, Tony Blair has "achieved so very little because of his gross efforts to please the Israelis."

It is also our view that Tony Blair's conduct in his private pursuits also calls into question his suitability for the role. Mr Blair has been widely criticised for a lack of transparency in the way he organises his business dealings and personal finances, and for blurring the lines between his public position as envoy and his private roles at Tony Blair Associates and the investment bank JPMorgan Chase.

With the current impasse in negotiations, it is time to rethink international engagement on the Israel-Palestine question. Alongside our call for you to remove Tony Blair as the Quartet special envoy, we are urging members of the public who feel the same way to sign the petition via the campaign website, sackblair.org.

Signed:

Mamdouh Aker, Palestinian Independent Commission for Human Rights

Mourid Barghouti, Palestinian writer and poet

Crispin Blunt MP, Conservative party

Professor Noam Chomsky, professor emeritus, Massachusetts Institute of Technology

Sir Richard Dalton, former UK ambassador to Libya and Iran

Professor Hani Faris, University of British Columbia

George Galloway MP, Respect party

Jeff Halper, director, Israeli Committee Against House Demolitions

Ken Livingstone, former mayor of London

Christopher Long, former UK ambassador to Egypt

Caroline Lucas MP, former leader of the Green party

Michael Mansfield QC, barrister

John McDonnell MP, Labour party

Sir Oliver Miles, former UK ambassador to Libya

Peter Oborne, writer and journalist

Professor Ilan Pappé, Israeli historian, University of Exeter

Rt Hon Clare Short, former secretary of state for International Development

Baroness Tonge, independent Liberal Democrat peer

Tom Watson MP, former defence minister, Labour party

Tony Blair's office has responded as follows:

"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.

"Mr Blair has done no work for JPMorgan in the Middle East – he is the chair of their International Advisory Council – where he provides advice on global political issues."