The families of British troops killed in the Iraq war vowed legal action Thursday against the long-delayed inquiry into the conflict unless it publishes its findings by the year's end.

The Chilcot inquiry was expected to take a year to report when it was announced by the government six years ago. It is looking at the decisions made in the run-up to the start of the war in 2003 and Britain's involvement.

Earlier this month, Prime Minister David Cameron criticised the delay to the probe, led by former civil servant John Chilcot, saying he wanted to see a timetable for publication.

The delay is linked to a process in which individuals such as former prime minister Tony Blair, who led Britain into the conflict, are given the chance to respond to criticism of them in the report.

A total of 179 British soldiers died in the conflict in Iraq between 2003 and 2010.

Matthew Jury, the lawyer representing the families, said there had been "outrageous delays" so far and voiced concern that these could be "interminable".

"The families are not content to simply wait forever for the inquiry to give a publication date and if Sir John does not impose... a deadline for publication, then we'll be seeking judicial redress," Jury told BBC radio.

Reg Keys, whose son Tom served in the British army and was killed in Iraq in 2003, said he thought the probe was skewed in favour of establishment figures rather than bereaved families.

"Iraq bubbles up in the headlines over the years and it's like an open wound continually prodded," he added on BBC radio.

"The only way for me to move on from this now is to consign Iraq to history and part of doing so is to get this inquiry published."

Chilcot insisted last month that his probe was making "significant progress" but could not give a timetable for publication.

Blair has insisted that neither he nor any of the main witnesses to the inquiry were the cause of the delay.