Ray Herring said the council would "redouble" efforts to protect data
A council has suspended all work with a contractor after a laptop containing personal details of almost 3,000 people was stolen.
Suffolk Coastal District Council has written to all those whose details were on the laptop, which contained names and addresses of licensing applicants.
The laptop was stolen from the home of a worker for Wiltshire firm LalPac Ltd.
The council said it was considering what further action to take over the "lapse of security".
It said the laptop was protected by a password, but the information it contained was not encrypted "so could potentially be accessed by an unauthorised person".
Ray Herring, the council's leader, said: "We had passed on to this company in an encrypted file the details of those who have been in touch with our licensing team.
"The company was employed by us to transfer this data onto a new software programme that we are using but this information is now potentially lost.
"The company has failed to prevent this data being taken home in an unprotected way and the theft of the laptop means that this information has been lost.
The company has failed to prevent this data being taken home in an unprotected way
Suffolk Coastal District Council
"We have instructed the company to stop the work they were doing for us and we are investigating what further action we could take against them for this lapse of security."
Mr Herring offered his "sincere apologies" to those whose details were on the computer.
The data includes information contained in applications from companies, organisations and members of the public for licences covering pubs, entertainment venues, taxi and private hire vehicles and for festivals and fetes.
In some cases, the council said the data would also include some details of those who had responded to consultations about licensed premises.
It stressed the data did not include any financial information.
LalPac said in a statement: "As soon as we learned of the theft, we conducted an internal investigation and notified Suffolk Coastal District Council.
"We have spoken to every one of our employees and a full internal investigation is now under way.
"We sincerely regret this unfortunate incident and would like to reassure the council and the people whose names and addresses are on the stolen laptop that we will do everything we can to ensure this remains an isolated incident. Our reputation depends on it."