EDINBURGH City Council has come under fire after its most senior official was encouraged to accept a second job as a non-executive director of utility giant SSE.

Sue Bruce, who has been chief executive of the council since 2011, will be paid £57,000 on top of her £158,533 salary, though she has pledged to donate some of the money to charity.

The move was approved by Andrew Burns, the Labour leader of Edinburgh council, despite his party's criticism of a similar arrangement last year when Lena Wilson, the boss of economic development agency Scottish Enterprise, took a directorship with a leading firm.

Yesterday the news was met with anger by Unison, Scotland's biggest public sector union.

John Stevenson, president of the union's City of Edinburgh branch, said: "When front line staff are pushed to the limit covering for staff shortages, it is not a good message that the chief executive has enough time to take on a second job.

"We trust that the decision to allow Sue Bruce to take up a second job with an energy company will herald a new approach by the council to all of its staff.

"In particular, we look forward to a more sympathetic approach to time off for staff doing unpaid trade union duties, and to staff on low pay who have no choice except to take a second job just to make ends meet."

Liberal Democrats on the council also demanded assurances over Ms Bruce's time commitment to SSE.

LibDem Councillor Paul Edie said: "I would want to be reassured we are going to get Sue's full attention on the problems of Edinburgh, which are not limited just to trams."

It is expected Ms Bruce will work for SSE for a day and a half per month on average. She will take up the role on September 1.

She promised to donate SSE fees to Edinburgh charities for as long as she is employed by the authority.

However some of the earnings may be used "to fulfil her obligation as a board member to purchase shares in the company," a statement from Perth-based SSE said.

Yesterday the former Aberdeen and East Dunbartonshire councils chief executive said she was "privileged" to join SSE. She insisted the move was a "mutually beneficial arrangement and a natural extension of the partnership approach that the council already has with many companies".

She added: "There is much from my experience that I hope to bring to the board, but the council's services can equally benefit through sharing the good practices of the private sector."

Lord Smith of Kelvin, the chairman of SSE, said: "It is often said that the public sector has much to learn from business. I believe the same is true in reverse and that Sue's experience and knowledge of the public sector will be invaluable."

The move follows anger a year ago when Ms Wilson took a £55,000 job on the board of London-based safety group Intertek.

At the time the appointment, endorsed by Finance Secretary John Swinney and Scottish Enterprise chairman Crawford Gillies, was strongly criticised by Labour and the LibDems.

Edinburgh City Council leader Mr Burns said yesterday he was "really pleased" about Ms Bruce's new role.

He said it was a "personal endorsement" and added: "I'm sure SSE will soon see the benefit of her contribution and that the council will gain from the perspective she will bring from her participation on the board.

"Sue asked me before accepting if I was able to give my support to her taking the appointment... I was happy to give her my backing."

The SNP – which is in coalition with Labour on Edinburgh City Council – also welcomed the appointment.

SNP MSP for Edinburgh Southern Jim Eadie said: "The fact senior public servants are clearly held in such high regard by the private sector should be seen as a positive. This 'attack the SNP now, think later' approach from Labour in the Scottish Parliament is sadly all too familiar and has backfired."

Edinburgh council employs 15,000 people and has a budget of more than £1 billion per year.