The Conservatives have described a Transport for London competition, to suggest ways to keep Tube passengers cool in the summer, as "a farce."

The £100,000 Cooling the Tube' competition, launched by the mayor in 2003, has been declared to have found no overall winner.

Ken Livingstone challenged the public to come up with an innovative and workable solution to cool the Tube - in what was the hottest European summer for 500 years.

A total prize fund of £100,000 was to be made available to any winner or winners.

But after 3,500 entries from 60 countries, it was decided that none of the solutions proposed an original or workable solution to the issue.

Tory assembly member Roger Evans said: "This is a classic example of a New Labour PR-stunt -an 'eye-catching initiative' - that delivers zilch. Meanwhile passengers struggle on in the heat of the summer."

"It's more about getting headlines than solving the problem," he told ePolitix.com

"This was a bizarre competition, Livingstone asked people all around the world for suggestions and now says none of them will work, its a bit like ask the audience."

Evans said the best way forward was to work on a system currently being trialled, which uses ground water as a cooling agent.

He said: "The water level has been rising in the underground anyway and if use can be made of it that would be great."

But he did admit the heat problem cannot be tackled over-night, and he said the London assembly Conservatives do not have a "magic wand" to solve it.

The criticism came on the day that Transport for London outlined its plans to help passengers 'beat the heat' while travelling round the city this summer.

In preparation for what are predicted to be hotter than average summer months, Tfl have promised £1m investment to tackle heat on the buses, continued investment in the Tube network and ongoing dialogue with Metronet and Tube Lines to find long-term solutions to tackling heat and improving ventilation.

Tfl has also launched its annual 'Beat the Heat' campaign which will issue advice through posters and announcements at all stations, including reminding passengers to carry water and not to board trains if they are feeling unwell.

The TfL five-year plan to continue addressing the issue of heat on the Tube will bring £10bn of investment to the underground system.

New trains to be delivered on the sub-surface lines will come with air-cooling, with the first trains due to arrive in 2009.

There will also be work on the 140 vent shafts on the Tube network and the provision of 30 per cent more fan capacity to get heat out of the system.

LU managing director, Tim O'Toole, said: "London Underground takes the issue of heat on the Tube very seriously.

"That's why we're now investing more than ever to tackle the issue.

"However, none of these projects will be quick, cheap or easy to implement," he added.