The Opposition leader has repeated his call for the prime minister to resign over the evidence produced at the Hutton inquiry.

Speaking after lawyers had given their final submissions to the investigation into the apparent suicide of former government scientist Dr David Kelly, Iain Duncan Smith said the ground already existed to justify his demand.

The Conservative leader said Tony Blair should accept full responsibility for the "shabby" treatment of Dr Kelly after the former Ministry of Defence employee came forward to admit to unauthorised contact with BBC journalist Andrew Gilligan.

"I think the charge stands hugely that the government has been spinning and lying its way out of this," he said on Thursday.

"The prime minister was at the centre of that and his position is untenable."

After a blistering attack on Downing Street and the MoD from Kelly family lawyer Jeremy Gompertz QC, Duncan Smith said the late government weapons expert had been thrust unfairly into the media spotlight.

"I agree with the Kelly family on this," he said.

"The government bears a responsibility in the way Dr Kelly's name came out. They have failed to act with decency."

Dr Kelly died in despair after being used as a "pawn in the political battle" between the government and the BBC, the Hutton inquiry heard.

Gompertz blamed the MoD and the media for the stress which led a "private and retiring" man to take his own life.

The lawyer said the actions of the government contrasted with the BBC "who have been prepared to admit to mistakes".

He said the government "made a deliberate decision to use Dr Kelly as part of its strategy in its battle with the BBC".

Geoff Hoon failed to take responsibility for a concerted effort "to out Dr Kelly" in a bid to undermine Today programme journalist Gilligan.

The hypocritical" and evasive defence secretary was guilty of a "cynical abuse of power", the inquiry was told.

Alastair Campbell's diary - which revealed the ferocity of the row between ministers and the corporation - was a "compelling document", the inquiry heard.

The diary revealed that the defence secretary had misled the inquiry.

"They indicate with clarity... that the secretary of state's denials of the government's strategy... were false," Gompertz said.

Gompertz, who adopted an aggressive tone during the cross-examination phase, said the Kelly family had been "hurt" by the actions of MoD personnel chief Richard Hatfield.

The claim that the MoD provided "outstanding support" to Dr Kelly would "were it not so serious. be risible" he said.

The media, however, had to shoulder some of the blame for the events which led to the death of Dr Kelly.

"Media attention upon an extremely private and retiring man should not be underestimated," he said.

Whilst he said the media at large had lessons to learn, Gompertz reserved special criticism for Gilligan - casting him as an "unreliable" witness.

In its closing statement, the government rejected all charges of wrongdoing in relation to the allegation that it "sexed up" the Iraq weapons dossier.

Representing ministers and civil servants, Jonathan Sumption QC said the allegations contained in Andrew Gilligan's report "could not be further from the truth".

Sumption also defended the decision to publish the now infamous 45-minute weapons claim.

"The process was as rigorous in the case of the 45-minute point as it was for all the material in the dossier," he told the inquiry.

The government's QC told Lord Hutton that Gilligan was not a credible witness and his story was both wrong and inconsistent.

The journalist's notes of the meeting with Dr Kelly, stored on a personal organiser, were dismissed as a "self-serving invention".

But he dismissed claims that Number 10 wanted all out war with BBC chiefs.

"The government is not, and never has been, engaged in a crusade against the BBC nor are any of the ministers or officials whom I represent," added Sumption.

Sumption also rejected that the government had "plotted" to unmask Dr Kelly.

The government's lawyer said the MoD was under no obligation to maintain Dr Kelly's anonymity.

"There is no constitutional principle that civil servants are entitled to anonymity," he said.

BBC counsel Andrew Caldecott QC conceded that Gilligan should have scripted a live broadcast which followed his report.

"Those who don't admit mistakes are unlikely ever to learn from them," he told the inquiry.

But he stood by the BBC's "entirely right" decision to broadcast its original reports.

Closing the session the respected law lord said he hoped to deliver the report "as quickly as a I can".

He added that this may be by late November - although it could drag on into December.