[6] In 2015, the Board of Deputies lodged a further complaint against Sizer, this time for posting a link accusing Jews and Israel of responsibility for the 9/11 attacks in the United States.

He began his career working for the Department of Health and Social Security (1971–1973) as a supplementary benefits visiting officer in east London.

I agree with him in rejecting the following errors which are held by many Christian Zionists: Lack of godly compassion for the Palestinians, and of concern for their human rights and about their legitimate aspirations.

[37][39] Hill believed posting the link could have been an accident, and insisted that Sizer "repudiates anti-Semitism and Holocaust denial" and was just drawing attention to an article about potential military action by Israel against Iran.

"[40] The then-backbench Labour Member of Parliament Jeremy Corbyn wrote to Andrew Hill, Sizer's bishop, around April 2012.

[40] The Board of Deputies of British Jews formally complained to the Church of England in late October 2012 over Sizer's actions since early 2010, under the terms of the Clergy Discipline Measure 2003.

[41][42] The complaint stated in part: "we will not remain quiet in the face of actions and remarks capable of being seen as antisemitic even where they are disguised as anti-Zionist attacks on Israel".

Jonathan Arkush, then vice-president of the Board of Deputies, told the BBC: "The thing that we did was to criticise him for publishing materials that were anti-semitic and anti-Jewish.

[45] In September 2014, by the invitation of Hamed Ghashghavi the secretary for international affairs of the "Second New Horizon Conference" Sizer attended the event in Tehran where 9/11 conspiracy theories such as "Zionist Fingerprints on the 9/11 Cover-up" and "9/11 and the Holocaust as pro-Zionist 'Public myths'" were under discussion.

A spokesman for the British Board of Deputies said that attending "such a hate-filled event is irreconcilable with his position as a minister in the Church of England".

[47] A few months later, on 20 January 2015 at 9.17 pm, Sizer posted a link on his Facebook page to a 9/11 conspiracy theory article entitled "9-11/Israel did it" on the WikiSpooks website.

Sizer, later apologizing,[48] clarified that he "never believed Israel or any other country was complicit in the terrorist atrocity of 9/11, and my sharing of this material was ill-considered and misguided.

[51] On 29 January 2015, the Church of England said in a statement that the comments made by Sizer were unacceptable and that the Diocese of Guildford would launch an investigation.

[55] On 9 February, it emerged that Sizer had been banned from social media by the new Bishop of Guildford, Andrew Watson, for at least six months for the Facebook post alleging Israeli responsibility for the 9/11 atrocities.

[58] The Church Times reported the bishop as saying that disciplinary action against Sizer had been considered, but an alternative approach was taken in order to resolve the matter quickly.

[60] In October 2016, Sizer attended a meeting organised by Palestine Return Centre at the House of Lords chaired by Baroness Jenny Tonge, which gained negative media attention for comments made during the session.

[63] In May 2022, a Bishop's Disciplinary Tribunal for the Diocese of Winchester hearing was held at St Andrew's Church, Holborn, London with eleven accusations being made against Sizer for antisemitism and causing profound offence to Jews occurring from 2005 to 2017.

[64][65] The tribunal's finding, published in December 2022, was that Sizer's conduct was "unbecoming or inappropriate to the office and work of a clerk in Holy Orders within section 8(1)(d) of the Clergy Discipline Measure 2003 in that he provoked and offended the Jewish community and/or engaged in anti-Semitic activity".

"[68] His barrister, Stephen Hofmeyr KC, later stated that “It is significant that not one word or statement from Dr Sizer has been shown to be antisemitic.

"[70] The Archbishop of Canterbury, Justin Welby, was quoted as saying "It is clear that the behaviour of Stephen Sizer has undermined Christian-Jewish relations, giving encouragement to conspiracy theories and tropes that have no place in public Christian ministry and the church.

An authority on antisemitism, Antony Lerman tweeted: "This disgraceful miscarriage of justice against someone who has never uttered a word of hate against Jews will be a permanent stain on the Church of England and the Board of Deputies.

[citation needed] Sizer has contributed articles for publications such as Evangelicals Now,[75] Third Way,[76][77] The Plain Truth[78] and Friends of Al Aqsa.