Carillion’s most recent finance director was a “whistleblower” who tried to expose the company’s accounting irregularities almost three months before the full scale of its problems were made public, new papers show.

Emma Mercer was six weeks into her job as finance director of Carillion’s construction services division when she raised concerns about the way the business was accounting for work on a number of major projects in April 2017, according to minutes from board meetings the following month.

Apparently not satisfied with the response she got from then chief executive Richard Howson or group finance director Zafar Khan, she took them up with human resources director Janet Dawson.

Her concerns, which focused on how profits were booked at major projects in Battersea and Liverpool, were then discussed at a number of board meetings in May. Alison Horner, chair of Carillion’s remuneration committee, “noted that Ms Mercer appeared to be a whistleblower who did not feel she was listened to”.

As a result of Ms Mercer’s concerns, the board was forced to consider whether its accounts for the previous year were still valid, and commissioned a review of the figures.

Andrew Dougal, chair of Carillion’s audit committee, said KPMG had not picked up the “sloppy accounting” when carrying out the audit of the company’s books.

However, the board rejected carrying out an independent review, instead asking KPMG to take a second look at the accounts as part of a review of contracts.

MP Frank Field, chair of the work and pensions committee which has been holding a joint inquiry into Carillion’s collapse, said: “That the next chief financial officer [Ms Mercer] had to go through whistleblowing procedures to get her concerns about accounting irregularities taken seriously by the Carillion board is extraordinary.

“So too is that the board’s response was to reject an independent review and get KPMG, their pet rubber-stampers, to mark their own homework.”

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The review concluded that Carillion’s 2016 accounts did not need to be restated, but the meeting minutes show that Keith Cochrane, who was later to become Carillion’s interim chief executive, thought that the findings “raised some fairly substantial questions around the ability to manage large contracts properly, and the broader question of culture”.

There was a “risk of over-optimism”, he told the board.

Peter Meehan, the KPMG partner in charge of auditing Carillion’s accounts, said he did not believe that there was “an intent to deceive”, but the discrepancies had arisen “due to incompetence, negligence or sloppy accounting”.

Ms Mercer, Mr Howson and Mr Cochrane, along with Carillion chair Philip Green, are due to appear before a parliamentary select committee on Tuesday.