Lothian Buses could be "bled dry" if it is put under direct control of an arms-length operator, according to a union.

Councillors will vote next week on whether or not to give Transport For Edinburgh (TfE) responsibility for the day-to-day running of the company.

Edinburgh City Council claims the move would help fully integrate the city's public transport system and develop the service "at a reduced cost to the public purse".

Unite said Lothian Buses workers fear the company would be "plundered" or sold off if the proposals are approved.

They will urge councillors to reconsider the plans with a deputation at the city's transport committee on Tuesday.

Unite regional officer Tony Trench said: "Lothian Buses is a jewel in the crown. It is one of the last remaining municipal bus companies in the UK.

"It is a profitable business that provides a good service for passengers in Edinburgh and beyond. We can't afford to have it threatened."

He said his members were concerned Lothian Buses would be used as a "golden goose" to plug gaps in other budgets.

TfE, which was set up in October 2013, holds the city council's shares in the bus company and helps develop an overall transport strategy for the city.

Lothian Buses has its own board and management, and reports directly to the local authority.

TfE also owns Edinburgh Trams, fuelling concerns that profits from Lothian Buses will be used to pay for an extension of the controversial project.

Mr Trench added: "This proposal opens a door and on the other side of it could be sell-off to a private bus company.

"And passengers know what that means - a poorer service, higher fares and no guarantee that routes will survive if they don't turn enough profit."

Several months ago, Lothian Buses took over the East Lothian bus system after rival firm First Group announced it was scrapping its service in the area.

Mr Trench said: "It was only because Lothian Buses is such a stable, profitable business that it was able to step in.

"Councillors in Edinburgh should be proud of Lothian Buses and shouldn't be handing it over to an arms-length company. We demand that they reject this proposal."

A council spokeswoman said: "We would recommend reading the Transport for Edinburgh governance report in detail - the council has committed to keeping Lothian Buses in public ownership and this report does not change this position.

"This report reviews the governance of Transport for Edinburgh, which is wholly owned by the council and aims to provide high quality integrated public transport in the capital.

"As part of this the report proposes Transport for Edinburgh develops business cases for a number of new public transport initiatives, which will be reported to council."