A new exhibition area for the British Museum, an extension to the Tate Modern and a mooted national film centre on the South Bank are all under threat as a result of government belt tightening.

Barbara Follett, the Culture Minister, told The Times yesterday that £22.5 million promised to the £135 million British Museum scheme in December 2007 was no longer guaranteed. “It’s very much on my mind,” she said. “Both the Secretary of State and I are in discussions with them. It’s a great idea and we would love to support it, but it’s very difficult at the moment.”

Other prominent developments could also suffer. “There are too many schemes bidding for too little money,” Mrs Follett said.

In December 2007 James Purnell, who was then the Culture Secretary, announced more than £70 million in state support for the Tate Modern and British Museum expansion schemes. “The arts matter because they can make people happy,” he said. “It’s also where society can find its meaning.”

Now, with the economy in trouble and Labour forecast to be out of office before either project reaches completion, priorities are changing.

“There are several excellent schemes that will help with the economy, would be a stimulus and will create more jobs and wonderful visitor attractions,” Mrs Follett said. “We just have to weigh them up.”

Tate Modern has received the first instalment of a promised £50 million towards a £215 million brick and glass extension that will increase space at the existing building on Bankside by 60 per cent. So far about a third of the total funds are pledged, more than half of it from the Government.

The British Museum’s Northwest Development is closer to a start date, with about two thirds of the money needed already raised, again counting the Government’s pledge.

Niall FitzGerald, the chairman of the trustees, described the museum this week as “shovel-ready to proceed in the autumn”, provided that the building receives planning permission from Camden Council at a meeting next Thursday.

The proposal drawn up by Graham Stirk, of Rogers Stirk Harbour and Partners, Richard Rogers’ practice, is backed by English Heritage and is expected to go through.

The new building is needed to host the museum’s impressive programme of temporary exhibitions. Shows such as the recent Shah ’Abbas exhibition and The First Emperor, which bought a detachment of the Chinese Terracotta Army to Bloomsbury in 2007, have been hosted in the Reading Room in the museum’s Great Court but planning consent for that arrangement expires in 2012 and is unlikely to be renewed, Mr Fitzgerald says.

A spokesman for the museum said that the development was essential and added that it would be a “great disappointment if the funding that has been promised was then not forthcoming”.

The British Film Institute has requested £45 million of government funding towards a £150 million multi-screen film centre. “We have had indications that we have mounted a very, very strong business case,” a spokesman said.

The organisation is, however, “incredibly aware” that the funding climate has changed since it first applied for support early last year.

The museums that the Department for Culture, Media and Sport (DCMS) subsidises directly have been told that their revenue funding will be cut for 2010-11. It has also warned Arts Council England and the organisations that it funds to expect a possible cut to their agreed grants for the same period.

A spokesman said: “Our capital budget is currently overcommitted. Ministers are examining the reasons for this and looking for solutions. It is possible that difficult decisions will be needed, but none has been taken yet.”

All three institutions are now likely to rely more heavily than they expected on private donors to realise their ambitions.

Mr FitzGerald said yesterday that the British Museum was happy to throw in naming rights to any of the new wing’s departments to help to flush out big donations. “It could be the Fred Bloggs exhibition centre, the Fred Bloggs conservation and research centre or the Fred Bloggs storage and handling area. If someone was really keen to have their name attached to another part of the museum we could do that as well.”

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