UK-Australia Free Trade Agreement

When we compare the original economic impact assessment of the Australia deal, which was released back in the summer, with the Government’s impact assessment published last month, we see that there has been a 1,000% increase in the estimated boost to UK GDP, but the small print makes it clear that that is because the Government have changed the economic model they are using to analyse the deal to one that produces a higher estimate of GDP. Can the Trade Secretary present any justification for this change, or is it simply a case of cooking the books?