Members of the Association of University Teachers are to hold a ballot on unity with Natfhe, the union representing college and university lecturers.
The decision was taken at the AUT's annual conference, when delegates applauded the decision after a lengthy debate.
Natfhe now plans to put an emergency motion to its annual conference next month asking for a full national ballot on unity.
If agreed by conference, the ballot would take place in the autumn, at the same time as a parallel ballot by the AUT.
Natfhe has 68,000 members, and the AUT 49,000. The intention is to dissolve both unions and establish a single body to replace them by 2006.
The new union, if agreed by both sets of members, would be the biggest union representing further and higher education staff in the world.
Natfhe's general secretary Paul Mackney said: "The AUT vote for a member ballot on a merger is a major step on the way to a new powerful voice for post-school education.
"I welcome this decision and hope that Natfhe's executive and conference will also put the proposed merger to members.
"Academic and academic-related staff want real shared ownership of developments in the system they work in. In a single union these staff will be in a much stronger position to fight for decent pay and conditions, and for high quality education for students."
AUT general secretary Sally Hunt said: "This historic decision to create a single union covering both higher and further education will put us in the driving seat to take post-16 education forward."
"Merging with Natfhes there will still be arguments about strategy, but they will take place inside the union and not through the media or in front of the employer."