Ian Clement is understood to have repaid all monies in full
Police are examining claims that an advisor to Mayor Boris Johnson misused a credit card following a formal report from the Greater London Authority.
The former deputy mayor for external relations Ian Clement quit over allegations of financial discrepancies.
An initial meeting between the head of financial services for the GLA and the police was held on Tuesday, members of London Assembly were told at a meeting.
Mr Clement admitted spending £2,300 on personal items with his City Hall card.
Among the expenses Mr Clement had used the corporate credit card for a £700 dinner in New York, a £535 stereo for his Jaguar and to buy £200 of groceries.
A Metropolitan Police spokesman said: "Officers from the Met's economic and specialist crime command have today received a referral from the GLA in connection with alleged misuse of expenses, which we will now be considering."
On Tuesday the GLA had contacted the force's Economic and Specialist Crime unit.
Earlier Martin Clarke, the GLA's executive director of resources, told the City Hall meeting: "A formal referral to the police will be held today. It will then be the police's decision whether to take that forward."
Only seven people have been issued corporate credit cards and the mayor does not have one.
The GLA had raised concerns about Mr Clement's use of the card in August 2008.
The mayor had asked him to give up the card after he learned that his deputy used it upgrade himself to business class on a flight to the Beijing Olympics.
He received further warnings from November onwards and earlier this month the card facility was removed.
Sir Simon Milton, deputy mayor for policy and planning, said he was "surprised" by the large amounts claimed by Mr Clement for entertaining.
"There was an imbalance in that it was quite clear that most of the people who were being entertained were Conservative politicians," Sir Simon said.
Mr Clement resigned after three Conservative councillors listed as guests in expenses claims denied eating out with him.
A GLA investigation found Mr Clement repaid all the money in full and made no overall gain.