Culture Secretary Chris Smith said details of the competition would soon be revealed as part of the government's commitment to ensure the dome had a lasting legacy.

Chris Smith: Staying silent on his ideas for the dome

The disclosure came as Mr Smith expressed confidence that vital public transport links to the dome site in Greenwich, south London, would be ready in time.

He also said the New Millennium Experience Commission's drive to raise private sponsorship to pay for dome attractions was on target.

"We have no intention of allowing the dome to become a failure," he told the House of Common's Culture Committee.

Preserving 'an icon'

Mr Smith said that the competition would ensure the dome was preserved as "a landmark and symbol for many generations to come".

"It's becoming an icon. It's becoming a building by which the world is coming to know Britain by," he said.

Mr Smith refused to be drawn on what his personal preferences were for the dome, saying he did not want to prejudice entries to the competition.

Confidence on rail link

He was more forthcoming on the subject of the Jubilee Line tube extension which is intended to bring large numbers of visitors to the dome by rail.

Transport links will be ready, Smith insists

The troubled underground project has been dogged by industrial disputes and stoppages.

But Mr Smith said he had every confidence that the "crucial bit" of the line between Waterloo and Greenwich would open in September.

Two other sections of the line would start operating even earlier, he said.

Mr Smith rejected suggestions from Labour MP John Maxton that this was "cutting it a bit fine".

The culture secretary also praised MNEC's fundraising for the dome.