The continued assaults of the resistance movement on the draft system may cause it to collapse before long, Michael Ferber, co-defendant of the Spock trial, said yesterday.

Ferber spoke at a Boston news conference, announcing plans for a New Mobilization Committee demonstration to be held Thursday at Government Center in support of the nation-wide Anti-Draft Week.

"The increasing number of resisters has burdened the government with a backlog of draft refusal cases and slowed the judiciary process. Over 500 people in the Massachusetts district who refused induction since December have not yet been indicted," Ferber said.

Stanislaw R. J. Suchecki, assistant U. S. Attorney for Massachusetts, added that about half of the 1968 draft refusal cases are still in various stages of examination.

Ferber, citing figures from his forthcoming book on draft resistance during the '60's, which he is co-authoring with Staughton Lynd, said that twice as many people were indicted in 1968 as in the previous year, but only 18 per cent were convicted compared to 48 per cent in 1967.

"1968 was a test year to see if the government would minimize convictions if the resisters were arrested in large groups. All those statistics show that though indictments increased, convictions fell appreciably," Ferber said.

Ferber also pointed out that the number of deserters in the Armed Forces rose by 50 per cent last year to 75,000 men Most of these deserters go to Sweden or Canada, though many remain in Saigon, he said.