ICE WILL ask its members this month if it should merge with the Institution of Mechanical Engineers.
But following the initial consultation, technicians, graduates and students will be denied the right to vote on any formal merger proposal.
Consultation will run between 31 May and 15 July. All members of both institutions will be asked whether they support a merger, oppose it or have no view.
'We're setting off on this partnership equally by asking members what they think - we're not prepared to waste time or money if it's not what the members want, ' said ICE president Colin Clinton.
Members will also be invited to email further comments and disclose their grade of membership.
But IMechE president William Edgar said that technicians, graduates, students and noncorporate members could only express their views during the consultation exercise.
He said they would not have the right to vote on any formally proposed merger.
He added that if non-corporate members backed a merger against the will of corporate members with voting rights, then a merger would not go ahead.
Detailed planning of how the merger could affect each organisation will only proceed if most of the two institutions' members back a merger during the consultation exercise.
Edgar added that a low consultation response would not affect interpretation of the results even if just 20% of members took part.