This week, Ms Lashley, 53, was dropped from the panel of approved Labour candidates following revelations earlier in the month about her convictions for prostitution and deception.
She will be unable to seek re-election for the party at elections next May after regional party officials decided her criminal past disqualified her as a candidate. She will also be barred from becoming Lord Mayor, even if she manages to retain her seat as an independent.
The party has said that her previous convictions for prostitution was not a factor. She was ousted because of her most recent court appearances on charges of forgery, counterfeiting, obtaining property by deception and conspiring to obtain a passport by deception.
Ms Lashley said yesterday that she was 'deeply shocked' and will be appealing against the decision.
She added: 'I have not received anything in writing but I have been told that my name has been taken off the panel. I plan to continue to do my work as a councillor for the Granby ward of the city council, and also carry on in the position of deputy Lord Mayor until my term of office expires in May.'
In April, senior Labour and Liberal Democrat councillors had anticipated Ms Lashley's defection at the council meeting of 27 April - one week before crucial council elections. The two parties finished with 44 seats each, and Labour has continued in power with support from independent Socialist members.
If Ms Lashley had defected, it could have put the Liberal Democrats into office for the first time in 10 years. She was unanimously elected deputy Lord Mayor at the council's annual meeting in May, and has refused to comment on her links with the Liberal Democrats.
Had she succeeded to the mayoralty next year, she would have been the first black person to hold a 788- year-old office whose incumbents have included Gladstone's father and the earls of Sefton and Derby.
But the revelations have diminished support for Ms Lashley, whose ward constituents were critical of her performance in local government before her criminal record was published by the Liverpool Echo.
Granby ward Labour Party said yesterday it would support Ms Lashley's appeal, but it is understood that one party official, who sought selection for this year's elections, is ready to take her place.
Granby includes the heart of Liverpool's black community. Local people allege discrimination in employment on the many construction projects in the area, most of them publicly funded.
Harry Rimmer, the council leader, yesterday confirmed he had tried privately to persuade Ms Lashley to relinquish the office of deputy.
'There was an overwhelming point of view being expressed by the Liverpool public at large that Petrona was now in an unsustainable position as deputy Lord Mayor,' he said.