The promotion and conservation of the Broads are set to be hit as the full impact of swingeing budget cuts on the authority which manages them became clear.

Nearly one quarter of the Broads Authority's 168-strong workforce will go over the next four years, with many of the 35-40 posts going as early as next April, although it is hoped to mitigate the effect by voluntary redundancy and early retirement.

Visitor centres in Beccles, Potter Heigham and Ranworth will close, with the authority retaining centres and boat trips at just three main hubs – Whitlingham Country Park, How Hill and Hoveton.

The authority's work in promot-ing sustainable tourism will be safeguarded for the next two years by European STEP funding, but beyond that chief executive Dr John Packman warned that the Broads Tourism Forum, its private-sector partner, would have to take the lead.

Just to keep the same level of waterways dredging and maintenance, presently subsidised by �200,000 of national park grant on top of boat toll income, boat owners are likely to face an average annual toll increase of 5pc for the next four years. This is the recommendation going to next week's Broads Authority meeting, at which the cuts package will also be discussed.

The grim impact of a 30pc cut in the authority's national park grant (NPG) from Defra over the next four years was outlined to staff at a meeting at its Dragonfly House headquarters in Norwich yesterday, ahead of a public announcement today.

The annual NPG is projected to fall from �4.4m to �2.96m, but the authority will only need to save �1m – one seventh of its total budget – because of the projected increase in tolls.

The cuts come at a time the Broads is bidding to boost tourism by being named as a world heritage site. The Broads Tourism Forum is leading a concerted campaign to rebrand it as Britain's magical waterland.

Dr Packman said that most of the upheaval of streamlining the organisation from four directorates to two by 2013 would be felt next April as it was felt better for staff to implement as much of the change as possible in one go.

He said: 'In implementing the cuts, we have sought to protect the frontline delivery of services by reducing the number of managers at all levels.'