Britain’s intelligence agencies are preparing to vet the final version of the Chilcot Inquiry’s report into the Iraq war ahead of publication this summer.

A team of security officials at MI5, MI6 and the Cabinet Office are expected to be given access to the two-million word document at the beginning of next week.

Some of the families of those who were killed in Iraq have expressed concern that the process could result in some of the key elements of the report being watered down. However, this has been categorically denied by both the Government and Sir John Chilcot himself.

Sir John said the checking process was a “necessary and normal procedure in inquiries that have considered a large volume of sensitive material”. He added its purpose was to ensure that the Government met its obligations under the European Convention on Human Rights and for the protection of national security.

The team who will carry out the vetting recently met John Penrose, the minister in charge of the Government’s response to the report, and is now said to be “all set” to start work.

Mr Penrose told The Sunday Telegraph that the process would take just two weeks to complete; however, the report would not be published until June or July because of the time needed to prepare it for publication and printing.

The delay may also be due to pressure from the Government not to publish such a controversial and distracting report before the referendum on Britain’s membership of the European Union.

“Nobody wants this to take any longer than it has already,” Mr Penrose said. “The process of checking by security officials will take no more than two weeks to complete. Sir John can then complete the process of preparing his report for publication on the timetable set out in his letter to the Prime Minister last October. We look forward to seeing the final report then.”

But Reg Keys, whose son 20-year-old son Lance Corporal Thomas Keys died in an ambush in Iraq in 2003, said he wanted to know who was going through the report and how ministers would ensure that embarrassing findings were not edited out.

Mr Keys added he was worried that there could be “cohorts of Tony Blair and Alistair Campbell going through” the report, adding the group had to be “politically neutral”. “There needs to be a referee almost – if someone says ‘I am taking this out', it needs to be shown to an independent person, otherwise it will be a whitewash,” he said.

Mr Keys said it was “absolutely absurd” that Sir John and the Government were sticking to a publication date of June or July to allow time for type-setting and proof-setting.

He said he was worried that the report’s publication would be overshadowed by the European Union referendum on 23 June. “If it is held up to after the referendum, it will be a ‘good day to bury bad news’," he said. "Does the Prime Minister want to be juggling two heavyweight news items at the same time?”

The news comes ahead of a House of Commons debate this week when MPs will put pressure on the Government not to allow national security vetting to delay publication.

The Iraq War: A timeline Show all 16 1 /16 The Iraq War: A timeline The Iraq War: A timeline 11 September 2001 Terrorists belonging to al-Qaeda use hijacked aeroplanes to kill 2,996 people in attacks on the east coast of the US. AP The Iraq War: A timeline 12 September 2001 Tony Blair promises George W Bush that the UK will support the US, whatever the President decides to do. AFP/Getty Images The Iraq War: A timeline 25 March 2002 Jack Straw, Foreign Secretary, warns Blair that invading Iraq would be legally dubious. Getty Images The Iraq War: A timeline June 2002 Tony Blair asks defence officials to outline options for UK participation in military action against Iraq. afp/getty images The Iraq War: A timeline 24 September 2002 The government publishes a dossier about the threat from Iraq’s weapons of mass destruction. A foreword by Tony Blair states that Saddam Hussein’s “military planning allows for some of the WMD to be ready within 45 minutes of an order to use them”. It is subsequently alleged that this dossier was “sexed up” for political reasons. Getty The Iraq War: A timeline 2 October 2002 Congress authorises President Bush to use military force against Iraq. Getty The Iraq War: A timeline 8 November 2002 UN Security Council passes resolution 1441, insisting that weapons inspectors be allowed back into Iraq and calling on the regime to give up its WMD or face the consequences. Simon Walker/AP The Iraq War: A timeline 18 July 2003 David Kelly, an expert in biological warfare, is found dead after being named as the source of quotations used by the BBC’s Andrew Gilligan to suggest that the dossier of September 2002 had been “sexed up”. Lord Hutton is appointed to chair a judicial inquiry into his death. GETTY IMAGES The Iraq War: A timeline 13 December 2003 Saddam Hussein is captured near Tikrit, after nine months in hiding. REUTERS The Iraq War: A timeline 2 March 2004 Bombings in Baghdad and Karbala kill nearly 200 people: the worst attacks since the fall of Saddam. Getty Images The Iraq War: A timeline 14 September 2005 Bombs in Baghdad kill 160 people and injure more than 500. EPA The Iraq War: A timeline 30 December 2005 Saddam Hussein is executed. Getty Images The Iraq War: A timeline 28 May 2009 The last British combat troops leave Iraq. Getty Images The Iraq War: A timeline 24 November 2009 The Chilcot inquiry holds its first public hearing. Getty The Iraq War: A timeline 2 February 2011 The Chilcot inquiry holds its final public hearing. AFP/Getty Images The Iraq War: A timeline 21 January 2015 Sir John Chilcot confirms that his report will not be published before the general election in May 2015. Getty Images

David Davis MP, the former Conservative shadow Home Secretary who is leading the debate, urged the Government to ensure the report is published as soon as possible. He said any delay was “frankly outrageous. This foot dragging has been going on long enough. The whole country is fed up waiting for answers".

Writing in yesterday’s Sunday Telegraph, Mr Davis wrote: "The families of those 179 British soldiers who died fighting for their country in Iraq have already waited long enough for answers. They have suffered for years as the inquiry has dragged on and on. Making them wait months longer, just because the Government is worried about what (if any) impact the report may have on the referendum, would be unspeakably cruel.

“This is not about pinning blame on people, it is about facing up to the mistakes we made as a nation. It is about giving those who have suffered great loss some solace in the truth.”

The Chilcot Inquiry started work in November 2009 and took its last oral evidence five years ago in February 2011.