TRAINS passing through an artificial tunnel in Belgium are being powered by sunlight from today, after 16,000 solar panels were installed on the roof of the 3.4km tunnel near Antwerp.

But critics say the installation has highlighted weaknesses in the British government's renewable energy policy. 

The tunnel, which covers the High Speed line close to the Netherlands border, was built to protect an ancient forest. Without it, some of the trees would have been felled to protect the line.

From today the panels are expected to provide enough power each year, an estimated 3,300 MWh, to power the entire Belgian network -- which is mostly electrified -- for a day, and in practice some of the current produced will be used at Antwerp Central station.

Solar panels will also be boosting railway power supplies in Britain from next year, when an installation on the roof of the new Blackfriars station in London comes into use.

But the firm which carried out the Belgian installation, which is reported to have cost £14 million, says the British government's reduction in support for more such projects would make them unviable.

A spokesman for the firm, Enfinity, said: "Apparently the UK Government is more concerned about the Treasury than mid and long-term carbon reduction objectives."

The government has reviewed its policy of funding large-scale solar panels, saying that they are too expensive. However, the Enfinity spokesman maintained that the costs of cells has halved recently in France and other countries, thanks to to the economies of scale.

The installation at Blackfriars, which will open next spring and should provide half the power used at the station, was funded by the Department for Transport's environment fund rather than general government subsidy.