The decision by John Prescott, the former deputy prime minister, to allow a skyscraper in south London, went directly against advice from his officials, it has been disclosed.

A departmental memo about the 50-storey tower in Vauxhall, made public under the Freedom of Information Act, shows that Prescott’s senior civil servants concluded:

“We do not believe the provision of affordable housing is adequate, as it comprises a disproportionate number of small units.

“Harm would be caused by the building to the setting of the Westminster World Heritage Site and a number of conservation areas. You are therefore invited to agree that the appeal be dismissed and planning permission refused.”

The 180m tower, by architect Broadway Malyan for developer St George, was given the go-ahead in July 2005.

Lambeth council had originally turned the scheme down, saying it was concerned about the proportion of affordable housing and the quality of the design. A planning inspector also backed that assessment.