He was replying to a calling attention motion of James Mathew in the Assembly, seeking necessary steps for registration of lakhs of migrant workers from others states in Kerala, under the Kerala Migrant Workers Welfare Scheme, 2010.
Ramakrishnan said only about 53,000 persons have been registered in the scheme so far.
"There are some practical difficulties for forceful registration of migrant workers," he said.
The accurate number of the workers has not yet been tabulated, he said.