Prince tried to influence hospital building policy and wrote to eight government departments in last three years

Prince Charles wrote personally to eight government departments in the last three years, documents obtained by The Guardian revealed today, prompting new accusations that he wields an undemocratic influence over policy.

Whitehall did not release the contents of the letters that Prince Charles wrote to at least eight government departments including the communities department.

In a separate report in the Times, it emerged that in 2007, when new prime minister Gordon Brown announced the creation of 10 carbon-neutral eco-towns, a charity set up by the prince urged then communities secretary Hazel Blears to adopt his favoured neo-Georgian housing design.

The Prince's Foundation for the Built Environment also wrote to health secretary Patricia Hewitt, to recommend that all hospital trusts should use their recommended design when planning new buildings.

The revelations are likely to increase the suspicion of the prince from parts of the construction industry, following the public spat earlier this year over his intervention in the Chelsea Barracks scheme designed by Richard Rogers. The prince wrote to the scheme's ultimate backer, Sheikh Hamad bin Khalifa Al-Thani, and Rogers was subsequently taken off the project.

Chris Huhne, the Liberal Democrat home affairs spokesman told The Guardian: “He has to be very careful to respect the traditional separation between the democratically accountable parts of the constitution and the ceremonial parts. The Prince of Wales is entitled to ask about what is going on but if he is urging a particular point of view, then that's a different matter.”