Gibbons issued a stock exchange bulletin on February 23 as they sought to raise £10m in a share issue.
The 160-year-old firm said previous auditors (Smith & Williamson) had left "because they consider the risks and uncertainties associated with the audit to exceed the level that they are willing to accept".
The services of Jersey auditors BDO have been engaged.
Gibbons' share price has collapsed across the past six months - nose-diving from £1.52 in September 2015 to just 46p last week - following a succession of increasingly gloomy financial posts.
Net debt levels have jumped by almost £11m to £22.6m with the company expected to post a trading loss of between £1m-2m for the full year to March.
Chief executive Mike Hall and chairman Martin Bralsford have cited a series of reasons for the poor performance.
These include "a weakness in our Asian operations and the continued illiquidity in high value stock items", problems with the launch of its website Marketplace and the "distraction of putting in place the right organisation structure and team to execute strategy".
The most recent filing said trading had been "particularly difficult in the interiors division" - the clutch of businesses under the umbrella of subsidiary The Fine Art Auction Group.
The London 'antiques department store' Mallett, acquired in October 2014 as Gibbons sought to diversify from stamps, have experienced a tumultuous 12 months. The lease on the firm's London showroom is currently up for sale for 'in excess of £2.5m'.
Stephan Ludwig, former managing director of the interiors and antiques division, who left the firm in September, is the subject of an unfair dismissal tribunal this month.
Smith & Williamson have not confirmed the detailed reasons for their departure.
However, Stanley Gibbons' vast inventory of stamps (with a 'book' value of around £55m) and its investment portfolio guarantees would be vulnerable to a market downturn of the type seen in the 1970s when a speculative bubble burst.
The company's philatelic investment products, guaranteeing customers at least 75% of the book value of their stamps at the end of a given period, are not approved by the UK financial authorities and lack regulatory protection.
Martin Peterlechner, group marketing director at Stanley Gibbons, told ATG the firm would be happy to respond to questions once the fundraising process is completed.