Mr Sundberg says Loch Ness is home to up to 60 families of monsters, and maintains his global underwater research team has no desire to hurt any creature.
Swede Jan Sundberg wants to catch a piece of the world-famous beast's skin for research purposes.
But his scheme to use a modified cod net have been met with deep concern.
Loch Ness investigator Dick Raynor has called for Mr Sundberg to be halted from his trapping attempt and branded the expedition "entirely unethical and ill-conceived".
Mr Raynor, who has probed the loch with underwater cameras, said: "I don't know if people take him seriously or not but my concern is he is planning to use a trap which could actually drown anything in the loch.
"There are grey seals in the loch which have come up the River Ness from the sea."
Mr Sundberg says Loch Ness is home to up to 60 families of monsters, and maintains his global underwater research team has no desire to hurt any creature.
Nessie comes under the Protection of Animals (Scotland) Act of 1912.
Inspector John Grierson, Northern Constabulary's animals officer, said it was an offence under the Protection of Animals Act for any person to do anything unreasonable which led to an animal coming to harm.
"If there is a monster and it is netted then it would become a captive animal and would be protected against any cruel activity," he said.
"But since it has not been proved that the Loch Ness Monster exists it is a fine legal point whether Mr Sundberg would actually be breaking any laws by simply trying to catch her with a net."
Gary Campbell, president of the official loch Ness monster fan club, said Mr Sundberg could be in trouble if any of the creatures were harmed.
"In addition he could fall foul of the Ness Fisheries Protection Board who look over the fishing interests in and around the loch. After all a net that size might catch a few fish."