The survey found that investment into the museum sector was down more than 17 per cent from £43m in 2004/05 to £35.6m in 2005/06. This is the third year in a row that investment has dropped. Revenues fell across all three investment types covered: individual giving; corporate donations; and contributions from trusts and foundations.

But Arts and Business said the figures were skewed by one major museum attracting far less money in 2005/06, although the organisation cannot be named for confidentiality reasons.

Across the whole arts sector, the figures for private investment were more positive. Private support has risen to £530m, its highest ever figure and up more than twice the rate of inflation. The biggest growth was individual giving, which is now £262m, while business investment is £153m and trusts and foundations contributed £113m.

The fall in private investment into museums comes at a time when the sector is becoming increasingly concerned about public funding and how it will fare in the next Comprehensive Spending Review. Arts and Business spokesman Jonathan Tuchner said there are different views on how a fall in public funding affects private investment.

'Some would argue that if a sector of the arts, including museums, receives less money from government, they will be forced to chase private money more forcefully and they might be successful,' Tuchner said. 'But Arts and Business has always said that if government is supportive of the arts and if it is healthy and buoyant, then it is likely that private sector money will follow.'

To press the case for continued long-term public investment in the sector, the National Museum Directors' Conference (NMDC) and the Museums, Libraries and Archives Council jointly commissioned a report - Museums and Galleries in Britain: Economic, Social and Creative Impacts.

The report, by Tony Travers of the London School of Economics, was published last month and has surveyed seven regional and 15 national museum organisations. The report builds on the research in Travers' 2004 publication, Valuing Museums.

Mark Jones, the chairman of the NMDC and the director of the Victoria and Albert Museum, is worried that museums' contribution to areas such as regeneration, tourism and social cohesion might be jeopardised by a fall in funding: 'We are concerned about the future in what is a very constrained funding environment. What museums need is stable core funding in real terms and it is only then that they can deliver all the things outlined in the report.'

Simon Stephens