A leading pensions lawyer is being drafted in to assist a parliamentary probe into the collapse of BHS, the high street retailer, amid a furious row about the stewardship of its 20,000-member retirement schemes.
Sky News understands that Robin Ellison, who serves as a trustee of several blue-chip pension funds, is being lined up to join a specialist panel being assembled by Frank Field MP, chair of the Work and Pensions Select Committee.
The appointment of Mr Ellison, a visiting professor of pensions law at Cass Business School, is expected to be announced ahead of the inquiry's first hearing on Monday, at which officials from the Pensions Regulator and Pension Protection Fund will give evidence.
Westminster sources said that Prem Sikka, a professor of accounting at Essex University, was also likely to be appointed to the advisory panel.
They will serve alongside Lord Myners, the former City Minister whose recruitment by Mr Field has intensified the sense of drama associated with the BHS investigation.
Both Lord Myners and Sir David Norgrove, the former pensions regulator and one-time chair of the M&S pension trustees, locked horns with BHS's former owner Sir Philip Green during his attempt to buy Marks & Spencer in 2004.
Sir David has also been enlisted by Mr Field's committee to support its work.
The appointment of the specialist advisors underlines the complexity of the MPs' inquiry as they attempt to unpick the details of how BHS's principal staff pension scheme went from being in surplus when Sir Philip bought the company to running a deficit of hundreds of millions of pounds when it was sold last year.
Sky News revealed on Saturday that the chief executive of the PPF would disclose on Monday that its estimate of the top-up cost to the pensions lifeboat would be between £250m and £300m.
In total, BHS's pension schemes have approximately 20,000 members, with 11,000 jobs at risk from the company's collapse into administration.
The PPF is sponsored by the Government but is funded through a levy on other defined benefit pension schemes, and steps in to protect the retirement benefits of insolvent companies' employees.
Schemes which are transferred to the PPF typically pay out 90% of the accrued benefits, with a cap on the maximum they can receive.
The PPF's £300m bill relating to BHS is just over half the £571m estimated cost of transferring the high street chain's pension schemes to an insurance company.
It is likely to be closer to the figure that the Pensions Regulator could ultimately seek to extract from Sir Philip Green, BHS's former owner, and other BHS stakeholders if they are deemed to have left its pension schemes under-funded.
The full buyout cost has sparked a furious row between MPs and Sir Philip, who this week accused Frank Field, chair of the Work and Pensions Select Committee, of pre-judging the outcome of their investigation.
The former BHS owner demanded that Mr Field stand aside from the inquiry.
Monday's hearing will be the first since the announcement of a parliamentary probe into the crisis at BHS, which called in administrators last month little more than a year after being sold Retail Acquisitions, the vehicle of an inexperienced group of executives, for £1.
Several inquiries have since been launched, including one by the Insolvency Service under the instruction of Sajid Javid, the Business Secretary.
