Domestic firms are heavily pessimistic in their business outlook for next month amid a prolonged economic slump and lackluster performance, according to the Federation of Korean Industries(FKI) on Thursday.

The federation's business survey index(BSI) of the top 600 companies by sales stood at 83-point-one for February, the lowest in two-and-a-half years.

A reading below 100 indicates that pessimists outnumber optimists. 

The BSI outlook for domestic firms has remained below 100 for the past eleven months since last April. 

The BSI for manufacturers reached 81-point-four, while the index for non-manufacturers, including restaurants, wholesalers and retail businesses, stood at 85-point-one, remaining below 100 for nine consecutive months.