Auditors have delivered a damning assessment of how a small district council in Surrey undertook the most expensive property investment ever made by a local authority. KPMG found “significant weaknesses” in financial processes surrounding Spelthorne Borough Council’s purchase of a BP research centre in Sunbury for £385 million in September 2016.

This raises further questions about billions of pounds of property investments which councils have made in recent years.

The decision-making process in Spelthorne was conducted via email and was “generally poor and difficult to follow”, meaning it was “difficult to identify whether all the risks associated with such a large and significant transaction had been fully considered and mitigated”, the auditor said.

The acquisition of the site, through £405 million borrowed from a government lending body, was decided by council officers without any public scrutiny using what is known as delegated authority. The Conservative-led council then took four months to publish the decision and in doing so incorrectly attributed it to the wrong council officer, said the auditor. Councils are required by law to issue such notices in a timely manner.