Mountford blamed rising costs and a failed summer range of casualwear, that has since been 'aggressively cleared', for the fall.
The business - which has 118 Moss Bros stores, as well as 18 Cecil Gee and 13 Hugo Boss shops - reported a like-for-like sales slide of 0.72 per cent, although revenue grew 1.4 per cent to£63.3 million.
The poor results, which had been expected, were preceded last week by the sudden departure of trading director David Pidgeon after he had only been with the company for six months.
Mountford said: 'The performance of Moss has not been satisfactory. The menswear retail sector experienced a generally challenging environment.
'These results have also been affected by a significant increase in property and utility costs, which disproportionately affect the first half, which has lower sales than the second half.'
He added that the outlook for the company remains 'challenging', but said that 'vigorous actions' had been taken to get the business 'back on plan'.
Commenting on trading, Moss Bros said that like-for-like sales had been flat in the first 10 weeks of the second half of the year and had 'not shown the growth in revenues we expected'.
The company added it had opened 9 Moss Bros stores in the half and that total operating costs had grown 5.3 per cent on the same period last year and fixed costs had risen by£1.1 million.
It has moved to a distribution centre in Barking, East London, after its Stratford site was closed to make way for the 2012 Olympics.