6.3 Official facilities and resources may not be used for the dissemination of material which is essentially party political.
8.4 Ministers must only use official machinery for distributing texts of speeches relating to Government business. Speeches made in a party political context must be distributed through the Party machinery.
Linking to the front page of the Labour Party website seems to Guido to clearly breach the rules.
The Cabinet Office issued specific guidance on 20 March 2008:
“Elections to Local Authorities in England and Wales and to the Greater London Authority – Guidance on Conduct for Civil Servants in UK Government Departments”
Under the heading “Communication Activities” it states…
“It is also important to take care with official websites which will be scrutinised closely by the news media and the political parties during election periods.”