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 today.

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 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 mainten-ance, 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 recommend-ation 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 water land.

Mr 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.'

They had also sought to strike a balance between maintaining their conservation function and Broads promotion work.

They would be looking to maintain to the same level their specialist work on fens management at such sites as How Hill and lake restoration at places like Ormesby Broad. However, he warned that the focus would have to be on sites acknowledged to be the most important.

Dr Packman said cuts would be felt across the Authority's staff, but job losses overall would be reduced by a raft of efficiency measures.

Savings would also be made by such measures as renegotiating its lease at Dragonfly House to occupy a smaller area of the first floor.

He said: 'We will not be able to carry out as many practical projects and will aim to maximise our impact by working in partnership on key projects. The recent restoration of Stubb Mill at Hickling is a good example with the work funded by Norfolk Wildlife Trust and the Heritage Lottery Fund.'

He said the Authority would be forced to cut back on its public events and focus on fewer high-profile ones at hub sites such as Whitlingham.

In the visitor centre shake-up, the Authority would be moving its solar-powered boat Ra from Barton Broad to Whitlingham, while its boat Liana would be offering trips from Hoveton.

He said: 'By focusing on three hub sites, we will be able to reach larger numbers of visitors and cover a larger proportion of running costs.'

He said they were negotiating with Waveney District Council to pick up tourist information at Beccles, and it was hoped Norfolk Wildlife Trust and the boatyards would do the same at Potter Heigham and Ranworth.

To keep up conservation work, the Authority would be looking to double its number of volunteers to 500 over the next four years. .

Responding to news of the cuts, Norfolk Wildlife Trust director Brendan Joyce pledged to 'do what we can to work in partnership with the Authority so that together we can tackle - with reduced resources - the many challenges we face'.

He added: 'We at the trust are pleased to see that the conservation work of the Broads Authority is to be retained, albeit at a more focused and prioritised level.'