KPMG has been fined a near-record £13m and severely reprimanded by an independent tribunal for misconduct, in a long-running case relating to the sale of the bedmaker Silentnight to a private equity group in 2011.

The tribunal determined that one of KPMG’s partners helped push Silentnight, which was a client of the blue chip accounting firm, towards insolvency so that the private equity group HIG could buy the business out of administration and dump the costly defined pension scheme for Silentnight’s 1,200 staff.

The government-sponsored Pension Protection Fund (PPF) is now calling for the fine proceeds to be used to plug any shortfall for Silentnight pension holders, who have been in limbo for a decade while investigations relating to the sale were carried out.

KPMG’s penalty is close to the UK record for a fine imposed by the accounting and audit regulator the Financial Reporting Council (FRC), which ruled last year that Deloitte should pay £15m for failings of its auditing of the software company Autonomy.

The FRC tribunal, which ordered KPMG to pay £2.8m in costs on top of the fine, found the firm and its former partner David Costley-Wood had a conflict of interest because they were acting for both HIG and Silentnight during the period in question.

Costley-Wood, the head of restructuring in Manchester at the time, was found to have misled the Pensions Regulator and PPF about what had caused Silentnight to run into financial trouble to help HIG in its pursuit of the business.

The tribunal ruled he was to be fined £500,000, severely reprimanded and barred from holding an insolvency licence or membership of the accountants’ professional body for 13 years.

“The scale and range of the sanctions imposed by the tribunal mark the gravity of the misconduct in this matter,” Elizabeth Barrett, the executive director of enforcement at the FRC, said. “The decision serves as an important reminder of the need for all members of the profession to act with integrity and objectivity and of the serious consequences when they fail to do so.”

KPMG has also been ordered to carry out an independent review to assess its policies, procedures and training programmes, and determine whether similar breaches might be found in a sample of past cases.

The Pensions Regulator, which originally referred the case to the FRC, said it was pleased with the tribunal’s decision. “Today’s announcement highlights the important role the audit, accountancy and actuary industry plays helping to safeguarding pension savers’ interests.”

The penalty comes months after HIG – which is headed by its founders, Sami Mnaymneh and Tony Tamer – reached a £25m settlement with the Pensions Regulator over similar allegations that it had deliberately pushed Silentnight towards failure to buy the company on the cheap. The proceeds of that settlement have gone directly to the Silentnight pension scheme.

The PPF, which runs pensions schemes for the staff of collapsed firms including Toys R Us and Austin Reed, wants the latest £13m fine to be put towards the Silentnight scheme as well. However, the money is destined for Institute of Chartered Accountants in England and Wales (ICAEW), which funds investigations carried out by the FRC.

“The FRC tribunal findings make clear the significant detriment caused to the Silentnight pension scheme, which is currently in PPF assessment,” the PPF said in a statement. “We believe it’s only right that the proceeds of the fines imposed by the FRC should benefit the Silentnight pension scheme so it can achieve the best possible outcome for its 1,200 members.”

The ICAEW said it had already received a request on behalf of Silentnight’s pension fund trustees but declined, saying it had the right to receive proceeds in return for funding investigations under the UK’s accountancy scheme rules.

Commenting on the ruling, KPMG said it acknowledged the tribunal’s findings and regrets that standards were not met. While it no longer provides insolvency services, KPMG said its “broader controls and processes have evolved significantly since this work was performed over a decade ago”.

It added: “As a firm, we are committed to the highest standards and continually invest in our people and procedures to ensure potential conflicts of interest are identified and managed effectively.”

HIG declined to comment.