The House Intelligence Committee on Thursday morning voted unanimously to release the transcript of its seven-hour interview with Glenn Simpson, the co-founder of the opposition research firm that helped assemble the controversial "Steele dossier," a source familiar with the vote told The Hill.

The vote comes on the heels of the unilateral release of the Senate Judiciary Committee's interview with Simpson by ranking member Dianne Feinstein (D-Calif.). House Intel Democrats have since been pushing for the release of the transcript of their interview, which took place behind closed doors in November.

President Trump slammed the release of the Judiciary transcript as "underhanded" and "possibly illegal," a claim that legal experts and lawyers dismissed as untrue.

Simpson's firm, Fusion GPS, has become a flashpoint in the national controversy over the dossier, a set of memos compiled by former British intelligence officer Christopher Steele and paid for in part by the Democratic National Committee and Hillary Clinton's presidential campaign that contained unverified allegations against Trump and his ties to Russia.

The source indicated the transcripts would post on the House Intelligence Committee website later Thursday.

The president's allies argued that Simpson's Judiciary testimony did nothing to undercut their core claim that the FBI had used the dossier to investigate Trump and possibly to secure a FISA warrant to spy on Trump officials during the campaign and transition.

Democrats responded by declaring that Simpson's testimony bolstered allegations in the dossier and Steele's credibility.

Olivia Beavers contributed.

Updated at 11:13 a.m.