Dec 13 (Reuters) - Belgian supermarket chain Colruyt on Tuesday reported operating profit of 123 million euros ($130.7 million) for the six months to Sept. 30, down 41.6% year on year, hit by high inflation and substantial cost increases.

The company, which competes directly with German discount retailers Aldi and Lidl, in September issued its third profit warning in 12 months, citing the impact of rising competition and growing costs from energy, transport and employee wages.

In Belgium, the wages of all workers are linked to inflation by law and Colruyt expects the greatest impact of the measure to be recorded the second half of the year.

"The months to come will remain very challenging, with gloomy macroeconomic forecasts that will further affect consumer spending patterns," CEO Jef Colruyt said in a statement.

Colruyt, which has operations in Belgium, France and Luxembourg, said its gross profit margin fell to 26.4% from 26.9% a year earlier because cost inflation was not passed on fully to the customer.

The group's net operating expenses climbed from 19.1% to 20.5% of revenue in the same period, the group said.

Colruyt shares have shed about 30% of their value this year. (Reporting by Diana Mandia in Gdansk Editing by David Goodman)