Miss Lawrence was last seen on March 18, 2019, at around 3.05pm at the junction of Heworth Road and East Parade, walking back towards her home on Heworth Road. She was also captured on CCTV as she left Goodricke College and as she walked home.
Miss Lawrence spoke to both her parents that evening over the telephone and was said to be in good spirits.
Her father, Peter Lawrence, reported her missing on March 20, after no one had heard from her and she failed to turn up for her 6am shift the previous day.
Police believe the then-35-year-old was murdered, but her body has never been found.
Mr Lawrence spent years campaigning for the Guardianship (Missing Persons) Bill, also known as Claudia’s Law, which allows relatives to take control of their missing loved ones’ financial matters.
The law was passed in April 2017 and came into force in 2019, however Mr Lawrence died last month without ever knowing what happened to his daughter.
Mr Dales said: "Despite the exhaustive efforts of (Claudia’s) late father Peter, family, friends and North Yorkshire Police, there are still no answers and it is tragic that Peter has died not knowing what has happened to her.
“More to the point in the light of there being no one brought to justice in the 12 years, there are still one or more people ‘at large’ in York or maybe somewhere else now who do know what has happened to Claudia and where she is and potentially remain a threat to the communities in which they and we live.”
Police previously said they “strongly suspect key and vital information” which would offer a breakthrough in the case of Claudia’s disappearance is being “withheld”.
Nine people have been questioned as part of the investigation, but no charges have ever been brought.
Jo Youle, chief executive of the charity Missing People – which Mr Lawrence worked closely with in campaigning for Claudia’s Law – echoed Mr Dales’s appeal for information.
“The search for Claudia continues and anyone who may have information regarding her disappearance can call or text the charity Missing People confidentially, and for free, on 116 000 or online at www.missingpeople.org.uk/sightings.”
Mr Dales also paid tribute to Sarah Everard, the 33-year-old marketing executive who went missing while walking home from a friend’s flat in south London on March 3. Her body was found hidden in an area of woodland in Ashford, Kent, on March 10.
He said: “All our thoughts and condolences go to her family at this time of great tragedy and with the general public in their support of the Everards, which was so evident also when Claudia went missing in 2009.
“If Peter were still with us he would have said this as, although he was often sad and depressed by Claudia’s absence, he was eternally grateful for the support of people in York, the UK and various parts of the world too.”
Anyone with information is urged to contact North Yorkshire Police on 101.