Sir Ian Wood has pledged £50m of his personal fortune to help create a visionary new city centre for Aberdeen - a beating heart for the community.

He hopes to create a street- level square - a cross between a grand Italian piazza and a mini-Central Park - above the under-utilised Union Terrace Gardens in the heart of his native city.

Some years ago a Scottish Enterprise survey revealed the graveyard of St Nicholas Church, where in the summer office workers enjoy picnic lunches sitting on the commemorative stones of generations past, is perceived as the "centre" of Aberdeen.

Sir Ian wants to create a hub, a focal point for future generations, which will draw together the retail and cultural aspects of the city.

Significant public and private funding is vital to make it viable and he hopes his contribution will be the catalyst to attracting the funding for the "North Sea oil-led transformational development".

"I am hopeful that others in the oil and gas industry might adopt this as their major contribution to Aberdeen's civic wellbeing," he said.

Serious reservations about the impact of the plan have been expressed by Peacock Visual Arts, which has planning permission for a £13.5m contemporary arts centre in Union Terrace Gardens. It fears any delay would lose it funding, there would be immediate redundancies and if the larger scheme fails the city could be left with nothing.

Sir Ian believes Peacock could benefit from being part of the larger project, although in a different position, but said if Peacock secures its funding and goes ahead as is, the city square project could not proceed. He said they were involved in constructive talks with the arts organisation.

Sir Ian has attached four conditions to his £50m offer. The street-level square must have a walk-on/walk-off from Union Street, Union Terrace and Rosemount Viaduct; it must cover the whole five-acre site including the Denburn railway line and adjacent roadway; it is subject to the outcome of the feasibility study which will determine the cost and scale of the project and also subject to significant public sector funding being available; and it must have the backing of Aberdeen City Council and the people of the north-east of Scotland.

"Aberdeen city centre has changed significantly in the last 30 to 40 years," he said. "In my young days, Union Street, with an east to west axis, was both the main retail centre and the heart - a high-quality main street which ranked among the best in Scotland. Sadly, it is now a shadow of its former glory.

"Aberdeen Beyond 2000', in the late-80s, first mooted the idea of raising Union Terrace Gardens to become a street-level city centre square. From a personal perspective, I consider the failure of Grampian Enterprise to achieve the backing and financial funds to achieve this in the early 90s to be my biggest failure as its first chairman and that has always bothered me.

"Over the past 10 years, there have been two other attempts at transforming Union Terrace Gardens, but both have failed due to lack of funds.

"Added to this is my conviction that the North Sea oil era, certainly the most economically rewarding in our city's history, should make its mark and contribute to some major transformational change in our city's core fabric.

"I see it as the people's square, something for everyone, and how it may be further developed both above and below ground is open to public debate. The new city heart should be an open leisure and recreational area with significant green landscaping, possible water features and certainly year-round cultural activities including leisure, arts and some all-weather facilities."

First Minister Alex Salmond, who attended the launch of the project, said that in tough economic times there was even more reason to have visions which transcended the current environment.

"Sir Ian's central point that the North Sea oil and gas industry should leave a lasting mark on the Granite City centre fabric is well taken. We should be excited by the scale of his vision and his commitment to ensure great things can be made to happen."