Wakefield Council today issued a statement saying it had terminated the contract with Heritage Building and Conservation (North) Ltd, as the company had failed to complete the project.
The firm was brought in to finish the work last year, after previous contractor William Anelay went into administration.
Andy Wallhead, the council's corporate director for regeneration and economic growth, said: “We are very disappointed and frustrated that Heritage Building & Conservation (North) Ltd has failed to deliver its obligations under the contract for the works at Pontefract Castle.
“There has been no work on site since mid-March and despite numerous attempts to contact senior managers we haven’t received any assurances that work will re-start. Because of this we have been left with no alternative but to terminate the contract and get someone else in to complete the work.
“Although we have not lost any money to HB&C (North) Ltd, we have lost time on what is an enormously important project for the council and Pontefract.”
The authority said it was working to appoint a new contractor "as soon as possible" and hoped work would still be completed this year.
The restoration project, titled the Key to the North, first got underway in September 2015.
The project's aim was to carry out conservation work at the monument, to take it off historic England's 'Heritage At Risk' register and open up parts of the castle, including the Sally Port, not seen by the community for many years.
Work ground to a halt in November 2016 when William Anelay went into administration.
But the project continued last March, when Heritage Building and Conservation (North) Ltd were drafted in - and a new visitor centre opened at the site last July, featuring a cafe, shop and museum space.
The Express has asked the council what work remains to be done.