Amazon and Tesco purchases on local authority card reviewed
A taxpayer-funded payment card was used at hotels and to pay for purchases at a pasty company and a collagen-based super food firm, records show.
Spending totalling more than £9,000 was now "subject to review" at Cambridgeshire and Peterborough Combined Authority (CPCA).
The Labour Mayor Nik Johnson is facing a separate investigation after a whistleblowing report.
Mr Johnson said he could not comment during the investigation.
In October, five months after Mr Johnson's election, an anonymous whistleblowing complaint was made in relation to behaviour and the use of a government procurement card (GPC), which is used by government and local authorities as a payment card.
The subsequent report, seen by the BBC, said an investigation into expenditure and expenses incurred by staff members at the mayor's office made "initial findings" that receipt and record keeping was "of significant concern".
It added: "No permission was sought, nor approval given for the use of the government procurement card or for officer expenses to be incurred for spend related to the Labour Party Conference."
Mr Johnson and his strategic advisor - who resigned in February - repaid money to address the card and expenses spend on the conference, the report said.
According to CPCA documents - some of which were published on the day the BBC asked questions regarding their status - at least £9,000 of GPC transactions between August and November are subject to review.
The majority of the expenditure under review is attributed to the mayor's office.
The CPCA documents state: "The transactions shown against a card in this report are currently under independent review, and it is expected that some of the expenditure reported will not ultimately be charged to the Combined Authority.
"Some costs have already been reimbursed to the Combined Authority."
More than half of the expenditure being reviewed was spent on hotels, including £1,730 at a Mercure Hotel on 26 September.
The Labour Party Conference took place in Brighton between 25 and 29 September.
Smaller purchases, such as from Amazon, Waitrose, Tesco and the St Ives Pasty Company, are also classed as subject to review.
Other expenditure under review includes a £1,499.80 spend on software on 17 October, as well as regular newspaper subscriptions and £84.99 on "SP So Body Co", understood to be a company which sells collagen-based "age-defying superfood".
CPCA documents link the purchase from SP So Food Co to the Economic Strategy division.
Mr Johnson said of the GPC spend: "I can't comment further whilst there is an ongoing investigation as I am fully committed to that process and would not like to do anything that could jeopardise the integrity of that process."
A CPCA spokesman said they would not comment on ongoing matters.
Find BBC News: East of England on Facebook, Instagram and Twitter. If you have a story suggestion email [email protected]