Intelligence on Iraq's supposed weapons of mass destruction may have been "marketed rather hard" for political reasons ahead of the 2003 war, according to the general who headed the Army at the time.

Speaking days ahead of Wednesday's publication of the Chilcot Report into the conflict, General Sir Mike Jackson said "the jury is still out" over whether the invasion had proved worth the cost.

Sir Mike was speaking as relatives of some of the 1 79 Britons killed in the Iraq War said they will boycott the inquiry over fears it will be a "whitewash".

The two million-word report, six years in the making, will be unveiled by Sir John Chilcot on Wednesday.

Tony Blair, prime minister when Britain went to war, has said he will not make any comment until the report is made public.

The International Criminal Court (ICC) has indicated the former Labour leader will not be liable for prosecution, reiterating its conclusion 10 years ago that the decision to go to war is not within its jurisdiction.

But the court said it will look at the report's findings before deciding whether there is a "reasonable basis" to begin an investigation.

A number of MPs are expected to try to use an ancient law to try to impeach the former prime minister once the findings are published.

Former Scottish First Minister Alex Salmond said there "has to be a judicial or political reckoning" for Mr Blair's role in the Iraq conflict while shadow chancellor John McDonnell said the "processes" of how Britain ended up at war must be examined "so we never ever get into this tragic, tragic mess again with such loss of life".

Asked whether he felt politicians lied to him about the case for war, Sir Mike told Channel 4 News: " No I don't believe I was misled.

"I'm certainly not going to say that this intelligence was fabricated - just made up. It may have been - how do you put it? - marketed rather hard for the political purpose that I can see. But I don't feel I was misled in the sense of being told lies, no."

Pressed over whether he lies awake at night wondering whether the war was "worth it", Sir Mike - who was Chief of General Staff at the time of the US-led invasion - said: "I've had that question in my mind from time to time yes."

He added: "I think the jury is still out as to was it worth it. It's very hard to answer that question to a mother who has lost a son or a chap without legs. It's very hard to answer that question."

Some of those whose loved ones died in the war and its aftermath between 2003 and 2009 fear the report will not give them the answers they desperately want.

Gary Nicholson, 42, was one of 10 servicemen who died when their Hercules C-130 aircraft was shot down in 2005.

His mother Julia said: "It will be a whitewash. I'm absolutely disgusted. I'm not going because it will be a whitewash.

"Tony Blair has got blood on his hands. He will have covered his back and (US President George) Bush's back."

Janice Procter, whose son Michael Trench, 18, was one of the youngest British soldiers to die in Iraq when he was killed in 2007, said: "It's been horrendous, I'm very apprehensive about this.

"This man (Blair) has put 179 kids to the slaughter - there's no justice.

"It (the report) is not going to give me any closure or comfort."

She added: "I'm not going down on the day, I'm not going to waste two hours of my life reading it."

The Chilcot inquiry was set up in 2009 by then prime minister Gordon Brown after the withdrawal of the main body of British troops earlier that year.

The inquiry examined decision-making during the lead up to the invasion and Britain's six-year military presence in the Middle Eastern country.

The long-awaited report draws on 130 sessions of oral evidence and the testimony of more than 150 witnesses as well as more than 150,000 government documents.

Relatives of the service personnel killed in Iraq between 2003 and 2009 will get an early sight of a 150-page summary.

David Godfrey, whose grandson Daniel Coffey, 21, was killed in 2007, said: "I'm quite apprehensive at the moment.

"People say this should bring closure but it won't. It might give us information but what we need is closure.

"It can't bring anybody back and won't stop us feeling what we feel. It's just another step forward on another long journey."

He branded Mr Blair a "war criminal" and said "he has to be held responsible".

Roger Bacon, whose son Matthew, 34, was killed in 2005, said: "It's been hanging over our heads - a great rock sitting over our heads and it wears you down, no doubt about it, and has worn us down for a long time."

He added: "What I'm expecting is that the report will bring out what I've always believed, which is that he (Blair) took us to war illegally.

"I have concerns about the way the troops were looked after when they were out there and the equipment supplied.

"The major thing is, how did we get into this mess in the first place?

"If it's a whitewash I will be hugely disappointed - no question of that."