Former BHS boss Sir Philip Green's rival Lord Myners joins probe into the failed store chain

Frank Field, who is in charge of the investigation into the collapse of BHS, has appointed Lord Myners to assist the Work and Pensions Committee in its inquiry into the collapse of the 88 year-old store chain. Myners, who fought off Sir Philip's attempted takeover of Marks & Spencer in 2004, has already raised questions in the House of Lords about the role of Sir Philip Green – BHS's former owner – in the store's collapse into insolvency.

Myners and Green are known to be long-standing rivals. In 2004, Myners threatened to sue Green for calling him an "anti-Semitic left-winger", but later decided to defuse the row after the retail tycoon had apologised.

According to the Telegraph, Sir Philip called Myners to ask why a public enquiry was needed. Myners, who had led a review of the Co-operative's board in 2014, explained that the committee needed someone "to ensure the right questions were being asked and that they were being answered fully".

Myners had criticised Green's role in BHS last week: "When Philip Green took money out of the company, he weakened the company and therefore weakened its ability to meet the pensions promise," he told the Guardian.

"If you have a company that is losing market share, losing profitability, heavily indebted, as BHS was under Philip Green's ownership, then the trustees should make sure there was sufficient money in the pensions scheme and they clearly failed to do that."

Field said Myners would lead a "panel of financial assessors to assist" his committee as well as the Business, Innovations and Skills Committee, who will hold their first joint session into the collapse of BHS on Monday, 9 May.

"A major aim of the Work and Pensions Committee representatives on Monday will be to test how adequately both organisations have carried out their duties to help protect members' pensions under the existing law, whether the existing law is inadequate and if so how should it be strengthened, or whether existing powers are adequate but were not fully exercised," field told the Telegraph.

BHS went into administration two weeks ago, 13 months after it was sold to Retail Acquisitions: a consortium led by Dominic Chappell, who has twice filed for personal bankruptcy.

Myners joining the inquiry comes a day after Green attacked Field for saying that the billionaire should pay £571m ($824m) to fill BHS's pension gap or "be stripped of his knighthood".