The singer Annie Lennox has made a scathing attack on plans for a £140m privately run park in the centre of her home city of Aberdeen, describing it as a "dog's dinner of crap concrete".

In a long post on her Facebook page, Lennox said the City Gardens proposals to build a large park and arts complex on a publicly owned park at Union Terrace Gardens would end up "ravaging the only authentic, historical green space in the city centre".

An Aberdonian by birth, Lennox's outspoken criticisms came after she read about the controversy in the Guardian's series this week on the privatisation of public land.

The project has divided the city: although it was backed earlier this year by 45,301 in favour to 41,175 against, in a referendum funded by its supporters, the Scottish Labour party won the largest number of seats in council elections on a manifesto pledge to oppose it.

Critics are worried about the need for the city to borrow at least £70m to build the City Gardens, paying it off slowly by raising extra business rates, in a city already struggling with heavy debts. Labour now runs the city in coalition with the Tories, and the council will hold a free vote on whether to allow it to go ahead in August.

In her post on Facebook, which generated dozens of comments, many critical of urban regeneration and building projects in places as diverse as Detroit, Philadelphia and Burnley, Lennox singled out the offer by Sir Ian Wood, the Aberdonian oil industry magnate, to give at least £50m towards the project.

Wood, the scheme's major backer, has said he could pay up to £75m if the project needed extra funds but has been fiercely criticised by opponents after he warned that if the project is rejected, he will spend that money abroad and not offer it to other public schemes in Aberdeen.

Lennox wrote: "From my recent visit to Aberdeen I was saddened and shocked to see how much decline has taken place. With so many windows boarded up in buildings and streets that used to 'thrive'.

"Weeds  … broken windows, dereliction and crappy shop front facades in the city centre of Union Street. It was once rather splendid … but sadly … no more. In the 'oil boom' town I saw little evidence of the trickle down of wealth.

"I've already expressed my views, and said very clearly that it is up to the citizens of Aberdeen to decide the fate of Union Terrace Gardens. The "vote yes" councillors' kneejerk reaction to the dangling £50m golden carrot is embarrassingly short-sighted.

"Another dog's dinner of crap concrete development, ravaging the only authentic, historical green space in the city centre is not the solution to the challenge of re-energising and revitalising Aberdeen. When will they ever learn?"

Lennox, who has had a series of hits as one half of the synthpop duo the Eurythmics and as a solo artist, criticised the development on her MySpace page two years ago after she heard that the City Gardens scheme would obliterate an alternative plan by the city's independent arts centre, Peacock Visual Arts, to build its own purpose-designed arts centre at Union Terrace Gardens.

Lennox then discovered that the promoters of the project had used a live photograph of her without permission in a brochure highlighting their plans to stage open air concerts in the planned development. The Press & Journal newspaper reported the brochure would be withdrawn.

Tom Smith, chairman of Aberdeen City Gardens Trust, which is leading the project, said it was designed to revitalise the city centre, and increasing the amenities and green space.

"We believe the problem that Ms Lennox has articulated is valid. It's well recognised throughout Aberdeen that we have a failed city centre and we need something which is going to be transformational," he said.

"I don't think we can afford to tinker around the edges. [The project] is not a silver bullet but we think this will be the catalyst for more investment and more regeneration of the city centre and the referendum backs that up."

Mike Shepherd, a campaigner with the opposition group Friends of Union Terrace Gardens, said that although Lennox no longer lived in the city she was entitled to oppose the City Gardens scheme.

"Annie Lennox was born and brought up in Aberdeen and obviously still cares passionately about the city," he said. "Her comments have been unprompted. She left the city to pursue a very successful career in rock music and she can't be faulted about that. Everyone is entitled to have an opinion about anything."