All correspondence from hon. Members and Peers is handled in accordance with the principles set out in ‘Handling Correspondence from Members of Parliament, Members of the House of Lords, MEPs and Members of Devolved Assemblies: Guidance for Departments'. The same principles apply when handling correspondence from members of the public.
The Cabinet Office, on an annual basis, publishes a report to Parliament on the performance of Departments in replying to Members ‘Peers’ correspondence. The report for 2006 was published on 28 March 2007, Official Report, columns 101-04WS.