Citibase, the serviced offices operator, has doubled its UK operation to more than 700 offices with the acquisition of six sites from Midlands-based Birkby.

The move is part of an aggressive expansion which will see Citibase open centres nationwide in the next five years. The group is now seeking institutional funding to help finance its programme.

In the deal with Birkby, Citibase will take over the leases of six centres in Manchester, Birmingham, Leicester, Bewdley, Leeds and Kenilworth.

Citibase will take 25-year leases on three of the centres at rents of £325,000 with £50,000 uplifts for the first two years and open reviews every five years. At the remaining three centres the company will sub-let the offices from Birkby.

As part of the deal, Citibase will pay Birkby an additional £250,000 in shares, equivalent to 15% of its equity. Birkby director Kim Taylor Smith will join the Citibase board.

Citibase currently runs five centres in London Victoria, Edinburgh, Bristol, Cambridge and High Wycombe. Office sizes range from 1,394 sq m (15,000 sq ft) to 3,250 sq m (35,000 sq ft). The new offices range from 2,320 sq m (25,000 sq ft) to 4,650 sq m (50,000 sq ft). The centres are let for a minimum of three months. Rents begin at roughly £600 pcm for a small office.

Citibase targets the local market with lettings to IT and recruitment companies, although blue chip clients include Microsoft, and Credit Lyonnais.

Target locations are city centre and peripheral business district locations.

David Joseph, joint managing director of Citibase, said: 'This is the first step towards achieving a nationwide network of business communications in which local enterprise can thrive.'

Kim Taylor Smith, chief executive of Birkby, said: 'The deal gives us a fixed rental stream whilst allowing us to focus on our core areas of activity – managed industrial Workspace and In-Shops. He added: 'The serviced office concept is very good – its just not a concept for Birkby.'