Museums opening under a massive cultural expansion could fail because of a lack of visitors, museums experts have warned.

More than 12 projects will open across the UK within the next six months as part of a £400m schedule funded by the Arts Council of England, the Heritage Lottery Fund and the Millennium Commission.

But there are fears that there will simply not be enough visitors to sustain the biggest programme of museum expansion in the UK's history.

Patrick Greene, president of the Museums' Association, believes the government will end up bailing out failing museums.

He said: "I think it is an urgent necessity at a government level to think through the problems and face up to them before this queue forms around Trafalgar Square up to the doors of the Department of Culture, Media and Sport."

The concerns are raised amid the publication of a highly critical report from a committee of MPs into the way the Arts Council is handing out lottery cash.

Of 15 major projects funded by the money, 13 are over budget and half are late - not good enough, say the MPs.

Culture Secretary Chris Smith is to launch the schedule of new openings.

The New Art Gallery in Walsall will be the first to open next month, designed by two of Britain's most controversial young architects, Adam Caruso and Peter St John.

Among the other flagship projects will be the long-awaited opening of Tate Modern at Bankside, London, which it is hoped will become one of the principal centres of modern art in the world.

Arts minister Alan Howarth said: "Tourism is a great sector, the number of visitors grows year by year. The creative economy is expanding very strongly in Britain.

"These are institutions which have an educational as well as an entertainment mission."

'Rich cultural heritage'

In April, The Lowry Arts Centre on Salford Quays in Manchester will open with a programme of performance and visual displays.

Nine further projects in May and June include a major new wing at the National Portrait Gallery and additional exhibition and education facilities at the Wallace Collection, both in London.

The Dulwich Picture Gallery in London will re-open after refurbishment, and the Science Museum's new Wellcome Wing will be opened, establishing it as one of the world's leading centres for the presentation of contemporary science and technology.

"This unprecedented season of openings is a tribute to the hard work of dedicated professionals in the arts who have devoted their time to expanding and improving access to the nation's rich cultural heritage," said Mr Smith.

"I am particularly pleased that so many excellent lottery-funded projects are now coming to fruition and are soon to provide stimulating and educative opportunities for all."

The announcement at the National Portrait Gallery in London also comes two days after this year's Museums and Galleries Commission annual report showed visitors to museum displays dropped by almost one million between 1997 and 1998.