[13] On 28th March 2024, he resigned as a Fellow of the Institute of Chartered Accountants in England and Wales,[14] and on 26 November 2024 he announced he would retire from Sheffield University Management School as of February 2025.
[23] Murphy claims that HMRC insiders have suggested to him that £300 million additional investment in the department could recoup £8 billion in unpaid tax.
[34][35] Corbyn also cited Murphy's estimate of there being £120 billion of missing tax revenue as part of the economic plan issued during his election campaign stating that this was enough to "double the NHS budget".
[36] In addition, Corbyn adopted several of the remedies that Murphy has advocated (including country-by-country reporting) to address this revenue gap.
[37] Murphy was notably not part of Labour's Economic Advisory Committee, which was set up after the leadership election in September 2015.
[38] Murphy was an informal adviser to Corbyn,[38] though it is reported that he had hoped to have a position on the Labour Party Treasury Team.
Corbyn had "not provided a vision of what his leadership will deliver", and concerning Labour's economic policies: "we have so far heard almost nothing that really progresses the ideas outlined last summer".
[41][42] In a response to a question raised in the House of Commons, Labour's Shadow Chancellor John McDonnell stated with regard to Murphy "He is not the economic adviser and never has been, because we doubted his judgment, unfortunately.
[43] Murphy is a vocal critic of Government Expenditure and Revenue Scotland as a report on the state of the Scottish economy.
He added, "25 of the 26 income figures in a set of accounts are estimates extrapolated from data for the UK as a whole and some consumer surveys.
"[44] At a subsequent appearance before the Holyrood, Finance and Constitution Committee, Murphy was however criticised for being unable to justify some of these claims.
[47] In 2001 Murphy wrote an article in The Observer recommending that parents set up a personal service company for their nanny, as an alternative to illegal cash-in-hand payments, to avoid income tax and national-insurance contributions.