Investors withdrew from Cardpoint yesterday after the cash machine operator counted the cost of buying its main rival Moneybox.
Cardpoint acquired its competitor for £90.5 million in August but said that budgets prepared by the previous Moneybox management were optimistic.
The Lancashire-based firm warned profits for the coming year may be lower than previously expected as business was hit by delays to the integration of Moneybox and the rollout of new ATMs.
Cardpoint was forced to reduce the value of Moneybox by £5.9 million as it said 1,000 of the 2,700 UK cash machines it had taken on in the deal would have to be scrapped or relocated.
The City reduced earnings forecasts for 2006 as shares fell 43 per cent or 55p to 71.5p.
Panmure Gordon analyst Charles Hall cut his profits forecast from £19 million to £8 million because of "the problems with the Moneybox estate".
Cardpoint said: "Although these matters are disappointing they are of a short-term nature and the strategic rationale for acquiring Moneybox remains compelling.
"The delay will have a detrimental effect on profitability in the short-term.
"However, these actions will contribute to increased profits in the future."
The warning came as Cardpoint posted pretax losses of £11.5 million for the year to September 30 compared with losses of £3.1 million last time, despite a 66 per cent increase in turnover to £61.1 million.
Pretax profits excluding the Moneybox deal were up 93 per cent from £1.9 million a year ago to £3.6 million.
The industry attracted widespread publicity and criticism after MPs began a highprofile investigation into the charges last year.
Cardpoint charges customers £1.50 to £1.75 per transaction at many of its ATMs, and in the last year added a further 290 dispensers to its fee-charging estate.
The 290 sites were among the 816 bought from Halifax Bank of Scotland in 2004, and Cardpoint said more former HBOS ATMs could be converted to the fee-charging model in the future.
Before the Moneybox deal Cardpoint ran 2,800 machines in places such as petrol stations and shops and dispensed more than £300 million every month.
Chief executive Mark Mills said: "Our customers are happy to pay a modest charge to enable them to withdraw cash from convenient locations.
"The amount of signage required to warn our customers of the charge that will be applied has been further increased during the course of the year."
On the more positive side for investors, the deal with Moneybox created annual savings of £2.4 million through 70 job cuts.
And Cardpoint also revealed that its purchase of cashpoints from HBOS cost £52 million - well below the £76.6 million expected at the time.