PORTLAND – CommTel, a Winthrop-based communications and technology company, said it is closing its Portland data services operation and laying off at least 15 workers.

The company blamed the move on the economic downturn, saying it made it hard to raise money to expand and sign up new business clients.

CommTel, a 104-year-old phone company that became one of Maine’s largest Internet service providers, expanded to Portland in 2000 through a group that developed Web sites. The company announced plans last June for a $45 million data center that would create as many as 200 jobs.

The project won the support of the city, which approved a $4.8 million tax break in October.

But soon after that, CommTel postponed construction and laid off 65 of its 160 employees.