The contenders include Hopkins Architects' Evelina Children's Hospital in Lambeth; Richard Rogers' Welsh Assembly; and a tree-top walkway in Northamptonshire designed by Forestry Civil Engineering.
Also shortlisted are Robin Snell's Water Activity Centre in Norfolk and Studio E's City of London Academy.
Prime Minister Tony Blair said: 'I congratulate all the candidates on the shortlist for this year's award.
'They represent, once again, a very diverse range of projects. But what they have in common is that each demonstrates a high quality of design and how this helps in the effective delivery of good public services.'
And CABE chair John Sorrell agreed. 'This year's shortlist shows the depth of quality we are now achieving across a wide range of public-sector building projects, including many with a complex, multi-functional brief,' he said.
'Following the recent launch of CABE's campaign to highlight the impact of bad design on people's lives and the waste of money that it causes, it is reassuring to see the public sector producing well-designed projects that improve public service delivery,' he added.
For a full list of the 13 shortlisted projects, visit www.betterpublicbuilding.org.uk.