Proposals to give officers at City Hall the power to splash out twice as much on property without scrutiny have been described as 'troubling'.
Currently, city council officers have authority to purchase buildings or businesses of up to £10m in value without consulting a committee.
However, they are asking cabinet members to agree to double this figure, allowing them to invest up to £20m on delegated authority, meaning even more multi-million pound investments could be made without the input of elected councillors.
Denise Carlo, leader of the Green group on Norwich City Council, said she had reservations about the proposals.
She said: 'I think it is very troubling that officers want to double the amount they can invest without proper scrutiny.
'They say this will give them more flexibility, but I don't believe this is a good enough explanation and large investments always present a big risk factor.'
Earlier this year, the council spent a combined £9.5m on two commercial properties - a cold store in Corby, Northamptonshire and a gym in Ramsgate, Kent.
Currently, 40pc of the council's commercial portfolio sits outside of its boundaries, on which it spent £13m.
The proposal comes as the city council looks to update the way it goes about investing in commercial property,
Ms Carlo added: 'I was pleased to see renewable energy listed in the type of things the council would invest in.
'However, I would certainly be concerned about the idea of investing in petrol stations or car parks, which are also listed.'
Paul Kendrick, cabinet member for asset management, said: 'If the recommendation is approved the process of purchasing commercial properties will remain robust.
'All councillors will continue to receive the property bid details and financial information in advance of completion and could call the decision in to scrutiny if they choose.
'We must ensure that we are a forward-thinking council with a proactive and ambitious approach to income generation so that we can help maintain the services that matter most to local people.
'The recommended rise in delegated authority to £20m would give us more flexibility so we can respond to opportunities as they arise in a timely and decisive way.'
The issue will be discussed by cabinet members on Wednesday.
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