As Prince Charles's letters are set to be released campaigners have repeated calls for the law to be changed - to allow for full disclosure of royal lobbying.

The law under which the letters will be released to the Guardian today was changed in 2010, which means no future request for disclosure can be successful.

Campaign group Republic has called on the government to repeal that change and to fully include the royal household within the Freedom of Information Act.

Republic's CEO, Graham Smith, said today:

"The government must now act to end royal secrecy. Any risk to the monarchy from disclosure must pale against a risk to democracy from having an activist prince acting in secret."

"These letters are only a small indication of widespread lobbying that's been going on for years.  We now need full disclosure and an assessment of his impact on government policy."

"We can't have a situation where we don't know what influence Charles is having on government policy."

"The changes made to FOI laws in 2010 must be reversed so future requests for disclosure can be successful."