The role of Voldemort was entirely played by Ralph Fiennes in “Goblet of Fire”.
The only actor credited with playing Voldemort on the IMDB page for “Harry Potter and the Goblet of Fire” is Ralph Fiennes. Richard Bremmer is not listed as having any role. He has also spoken about passing on the role of Voldemort to Ralph Fiennes for Harry Potter and the Goblet of Fire, who would be playing Voldemort in the fourth movie.
Bremmer told This Is Northeast, "The producers spent a long time fighting to get me so I'm very proud to have been the first. But the role is now being played by Ralph Fiennes, who is an old mate, in the fourth film.
"I've been in the business a long time and it didn't surprise me they just went for a bigger name, being Hollywood led, and I'm happy to pass it on to Ralph."
- Bremmer speaks about 'Harry Potter' (digitalspy.com)
This would be strange for Bremmer to say if he was still partially in the role of Voldemort by voicing him before his body is restored. Additionally, the version of Voldemort before he is restored to a body is modeled on Ralph Fiennes.
MPC took over for the shot where Voldemort grows from and out of the cauldron. We divided the shot into separate elements: the cauldron, the cauldron smoke, the cloak smoke, the cloak, the fire, the slime, the drips and Voldemort, Aithadi relates. Voldemort alone was quite complex as the effect included skin, wet skin, bones, organs and muscles. We used a cyberscan of Fiennes as a base to model the baby Voldemort.
- 'Harry Potter and the Goblet of Fire': Part 2 — Wizard Competitions, Deatheaters and Voldemort (awn.com)
Therefore, it is a logical conclusion that Ralph Fiennes was the only one to play Voldemort in “Harry Potter and the Goblet of Fire”.