But Culture Secretary Tessa Jowell has warned the museum that its government funding - worth £38m ($58.8m) a year - could come under scrutiny if it abandons its policy of free entry.

Visitor numbers at the South Kensington museum have soared by 70% since charges were dropped last December, in line with the Department for Culture, Media and Sport's flagship policy.

Visitor numbers have soared

Museum bosses have told MPs the extra volume of visitors is costing them £500,000 ($773,000) a year more than they receive in return for giving up charging.

Director Sir Neil Chalmers said he was not prepared to see the museum "damaged by lack of funding".

He said it was up to the trustees of the museum to make the final decision.

Strings attached

Ms Jowell told the Commons Culture Select Committee the museum would receive a funding boost as part of a settlement worth £70m ($108.3m) to museums and galleries across the nation.

But she rejected the idea that the museum may go back to charging.

Ms Jowell told the committee that museums were "publicly funded bodies" and that the money they received came with "strings attached".

"One of those strings is that they maintain free entry," she said.

Tessa Jowell opposes charges

The Natural History Museum was one of the few institutions that opposed Labour's policy of free access to nationally-funded museums.

Since lifting its £9 charge, it has seen visitor numbers increase from 1.7m to 2.3m a year.

The growth in numbers has not been reflected in takings in its shops and cafes, however, and extra staff have had to be hired to cope with the crowds.

Mrs Jowell said she believed the museum's financial problems were due, instead, to a drop in visitors to London since 11 September and the foot-and-mouth epidemic.