Miss Ladele said she was accused of being homophobic
MP Diane Abbott has tabled a Commons motion urging a law change after a registrar won the legal right not to carry out same-sex civil partnerships.
Last week, a tribunal ruled Lillian Ladele was harassed and discriminated against by Islington Council for refusing to carry out gay "weddings".
But Ms Abbott said public servants should not be allowed to discriminate because of their personal prejudices.
This comes a day after the council said it would appeal against the ruling.
Ms Ladele said the civil partnership ceremonies went against her Christian beliefs and hailed the decision as a "victory for religious liberty".
Ms Abbott is urging Ministers to amend the law if necessary to ensure that the public are treated equally, and not discriminated against because of what she called "self-defined religious beliefs".
Miss Ladele took her case to an employment tribunal after claiming she had suffered bullying and ridicule as a result of her stance.
She said she held orthodox Christian beliefs about marriage and could not carry out same-sex unions "as a matter of religious conscience".
Councillor John Gilbert said: "This isn't a decision [appealing against the ruling] we've taken lightly, but we believe an important question is at stake and the law must be clarified.
"Islington Council, like all councils and employers, needs to know whether we can expect employees to provide services to all sections of the community, regardless of who they are."
Mike Judge, at The Christian Institute, said: "No couple was denied a service by registrars.
"Most couples said that they received a first-class service."
He said it was about "wanting to get rid of Lillian Ladele because of her religious beliefs".
"It was not personal but ideological. Christians have rights too," he said.
Until December 2007 registrars in Islington worked on a freelance basis but since then they have been under direct control of the local authority.