A Treasury spokeswoman confirmed that this was a permanent role and Ellison will be a special adviser to the Chancellor, Philip Hammond. She took up her new role this week.

Ellison was financial secretary to the Treasury for a year until the election was called in April 2017 but lost an 8,000-vote majority at the last election, having first won the Battersea seat in 2010 with a majority of around 6,000. Labour candidate Marsha De Cordova took 25,292 votes to Ellison's 22,876 - a majority of 2,416.

The appointment of Ellison follows a major shake-up of senior Treasury posts as David Gauke, number two in the Treasury, was moved to the Department for Works and Pensions (DWP) as secretary of state for work and pensions in the recent reshuffle while Ellison losing her seat meant that Mel Stride, Conservative MP for central Devon, was appointed to replace her as Treasury financial secretary.

Gauke was replaced by Liz Truss as chief secretary to the Treasury, moving from Justice where she was secretary of state. Truss is a CIMA member and accountant, who worked for Shell, Cable and Wireless and was deputy director of think tank Reform before becoming an MP.

The overhaul of key posts at the Treasury means that much of the tax expertise at the top of the Treasury was hollowed out.

Making Tax Digital and a truncated Finance Bill, with a raft of tax measures effective 6 April and not even legislated for, are top of the agenda for the new Treasury team, there were particular concerns from the profession that the loss of Ellison, who had been in position for two years, would mean that there was a vacuum of understanding about Making Tax Digital at the Treasury.

The digitisation of quarterly reporting – the Making Tax Digital programme - is due to go live for unincorporated businesses over the VAT threshold of £85,000 from April 2018. There are still concerns that HMRC has overestimated the effectiveness of Making Tax Digital as the main tool to close the tax gap, currently estimated at £40bn.

Ellison is respected in the tax profession for making efforts to get to grips with Making Tax Digital and reaching out to advisers and the institutes during her year as financial secretary to the Treasury since her appointment in July 2016.

Prior to becoming an MP, Ellison worked for John Lewis in various marketing roles, joining from university having studied philosophy, economics and politics (PPE) at Oxford. She also served as a local councillor on two separate occasions in the London Borough of Barnet.