THE writer of an acclaimed film that savages Britain's welfare regime has accused the UK Work and Pensions Secretary of talking "guff" during a showdown with MSPs.

Paul Laverty, the Scot who penned I, Daniel Blake, escalated a war of words between the film's creators and Damian Green after watching the minister reject claims that the benefits system had driven people to suicide in an appearance at the Scottish Parliament.

During a fraught evidence session with Holyrood's social security committee, Mr Green was given a signed copy of the script of the film which he has previously criticised as a 'monstrously unfair' work of fiction despite admitting he has never seen it.

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Mr Laverty attended the session, the first time ever a UK Work and Pensions Secretary has appeared before a Holyrood committee, while a campaigner in an I, Daniel Blake t-shirt sat directly behind the minister in the public gallery. The controversial film tells the story of a 59-year-old joiner who has a heart attack and finds himself caught in a nightmarishly complex struggle over benefits.

Afterwards, Mr Laverty accused Mr Green of "an absolute and total whitewash" during questioning and failing to acknowledge the reality of the "terrifying" impact of benefit sanctions on the lives of the vulnerable.

The writer added: "That was a public relations exercise, it's absolutely guff. Two days ago Mr Damian Green described our film 'as having no relationship to the modern benefits system' and 'monstrously unfair' to the job centre staff. Then he admits he hasn't seen it.

"I travelled the whole country, spoke to whistleblowers within the DWP, activists, academics and people in foodbanks. What we saw was people's lives thrown into absolute chaos by the sanctions regime. When he says our film has no resemblance to reality, it does make my blood boil.

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"The characters in the film are fictional, but are informed and inspired by everything we saw during some serious investigation."

Mr Green was repeatedly challenged by MSPs over benefit reforms and the sanctions regime which can see claimants' payments suspended if they do not follow strict rules.

He declined an invitation to apologise the "significant failures and problems" of the reforms since their 2010 roll-out, saying the policies were aimed at helping people "take control" of their lives while describing sanctions are a "necessary backstop".

SNP MSP George Adam presented Mr Green with a signed copy of the Daniel Blake book as "light reading" for his journey back to London. He added that campaigners who had previously given evidence to the committee had "almost" accused Mr Green of murder due to suicides that had taken place due to the stresses of the benefits system.

A visibly irritated Mr Green replied: "There is no evidence, and I think bringing people who committed suicide into political debate is always unfortunate. Clearly every suicide is a tragedy, there are complex reasons behind everyone, and as I say to try and politicise individual tragedies like this always seems to me to be very unfortunate."

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He added: "It is absolutely not the intention of anyone connected with the welfare system, whether it's ministers or staff of the DWP, to cause distress. The system is there to help people and I see it as an essential part of my job to try and set up structures and set up the organisation of the system so that it is there to help."

Sanctions, he said, have fallen in the last year, with Scotland seeing a 60 per cent fall in Jobseekers' Allowance sanctions in the year to March 2016. Aspects of the welfare system are being devolved, with the Scottish Government saying it intends to put an end to the current sanctions regime north of the border.

"Absolutely I think they need to be there, but also they need to be there only as a last resort," he said.