In November ACE announced plans to relocate the ENO as a national portfolio organization.
The public body proposed that ENO would receive a £17 million grant over three years, but only if it moved outside London with the suggestion of relocating to Manchester.
In April, it was announced that the opera company would receive funding of up to £24 million from ACE, to help with the relocation.
An event on Thursday saw members of entertainment trade unions Equity and musicians. Milan assembled to hear the resolution passed.
It proposed no job losses at ENO as a result of the funding cuts and demanded that Arts Council England “end its requirement for ENO to establish a primary base outside London”.
Equity, which is representing chorus and stage management workers at the company, fears the relocation will lead to redundancies and creative workers being re-hired on indefinite freelance contracts.
Proposing the motion, Londonwide Assembly member Ellie Baker said: “I am delighted to put forward this motion to protect the unionized workers who form a vital part of London’s economy and the culture in our city.
“By adopting this motion today, the London Assembly will make clear to the Arts Council that they need to stop their ill-conceived plan to relocate ENO out of London.”
She continued: “The impact on the lives and livelihoods of workers at ENO is clear. Family And careers hanging in the balance for months, this needs to stop.
“The chorus and stage management workers at ENO deserve better the Arts Council than this rash decision.”
“The Arts Council must listen to the concerns of the London Assembly, expressed and cross party support received in our proposal this afternoon, and I look forward to the offer of a meeting with ACE Chief Executive Darren Henley to address our concerns I’m doing it.”
A recent survey of equity members working at ENO revealed that more than two-thirds of staff would leave the company and the profession if it relocated outside London.
Members cited relationships that include children in school, caring responsibilities and partners with jobs in the capital.
Thursday’s proposal also called Mayor Sadiq Khan of London to intervene with ACE and the Secretary of State for Culture on the proposed move.