The mum-of-four, who was 41 when she vanished, was last seen parking her car in Alvescot Road while on her way to work at Swindon College in March 2002.
Razzell, a former insurance investment manager from Crewkerne in Somerset, made appeals in the news for her return but was later arrested and charged with her murder.
Linda, originally from Llanybydder in Wales, had been in the midst of divorce proceedings and had visited a bank with a court order to freeze her husband’s bank accounts the week before she vanished.
Detectives found traces of blood in the boot of a car Razzell had used.
When the Parole Board approved Razzell’s release on licence in April, it said in a statement that the “panel was satisfied that imprisonment was no longer necessary for the protection of the public”.
The Ministry of Justice (MoJ) referred the decision to the High Court – a move the agency can do if it believes a prisoner’s release would undermine public confidence in the parole system.
During a two-day hearing at the High Court earlier this week, barristers for the MoJ said the Parole Board had failed to assess Razzell’s risk properly and called for the decision to be reversed.
Linda’s relatives also urged the court to block his release.
Her cousin, Julie Westmore, said she would not “feel safe” and expressed fear that “all hope of ever finding [her] remains will be lost” if Razzell was released.