The estimated policing costs for the Liberal Democrats' autumn party conference in Brighton will be £2.1 million, it has been disclosed - but tourism chiefs expect it to bring in £15 million.

Around 8,000 delegates will flock to the seaside city for the event which starts on Saturday.

Fencing has been erected around the conference's venue, the Brighton Centre on the seafront, but the scale of the security operation is smaller than previous years.

The cost of the Labour Party conference in Brighton in 2009 amounted to around £6 million, substantially less than the £2.1 million cost predicted for the Lib Dems' event.

Niall Griffin, the deputy planning co-ordinator for Sussex Police, said: "We have taken police officers over and above the normal policing requirements and we have also brought in officers from other forces to enhance our numbers."

Mr Griffin said police were expecting a "safe and peaceful" protest on Saturday by campaigners from groups including Brighton Stop the Cuts and the local Trades Council.

Adam Bates, head of tourism and leisure for Brighton and Hove City Council, said the conference should boost the local economy by an estimated £15 million. He said: "It has been a tough summer. The early poor weather didn't help and the general economy is making it very difficult for many businesses.

"That said, we are a city with a lot going on and better than most. It's great to have (the Lib Dems) back. There is a lot of competition as we have relatively new venues in Liverpool, Manchester and Glasgow."