The former Conservative MP said the judgement that the company were wrong not to bake the cake for a gay customer was "legal nonsense".
Ashers declined an order placed by gay activist Gareth Lee, claiming the message was inconsistent with their religious beliefs.
Last year, it was found to have breached equality legislation following a high-profile court case in Belfast.
A hearing at Belfast's Court of Appeal in October backed the judgement.
Through the legal proceedings, Daniel McArthur, the company's general manager, insisted Mr Lee's sexuality was never an issue, rather the message he wanted the bakery to create.
In an article for the Daily Express Widdecombe added: "If a heterosexual couple or a single person had come in to the shop and asked for the same slogan to be put on a cake the bakers would still have refused.
"If the homosexual couple had asked for a cake emblazoned happy birthday it would have been made.
"Thus it is illogical to suggest that the issue was the sexuality of the customer rather than the slogan itself."
She said that "Britain now comprehensively fails" when it comes to the ability of an individual to exercise freedom of conscience.
"This is what we have come to. Once regarded as the very bastion of liberty and freedom of speech, Britain now sets an example that other countries want to avoid.
"Oh, woe that we, whose parents gave life and limb for liberty, should have witnessed such a day."