Judge Shreeshananda rejected the anticipatory bail plea of the Hospet MLA, an accused in Belikeri mining case.
CBI probing the case has intensified search operations to apprehend Singh, who is believed to be in Singapore, agency officials said.
There is already a lookout notice issued to all police stations by the CBI, they said.
CBI had summoned the legislator for questioning in September but he had failed to turn up and fled reportedly to Singapore from where he filed an anticipatory bail application before the CBI court on medical grounds, fearing arrest.
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Three MLAs - B Nagendra, Suresh Babu and Satish Sail- have already been arrested in the case.
The illegal export from Belekeri port in Uttara Kannada district was exposed by former Karnataka Lokayukta N Santosh Hegde, who in his report, had said 7.74 million tonnes of iron ore were illegally exported between 2006-2007 and 2010-11, causing huge loss to the exchequer.
Those in custody include two former IAS officers and two Indian Forest Service officers.