FACTBOX-The government's 42-day detention plans

LONDON (Reuters) - The House of Lords votes on Monday on government plans to allow police to detain terrorism suspects for up to six weeks without charge.

Here are brief details of the proposals:

- The new powers will apply only when there "is a grave exceptional terrorist threat" such as an attack on Britain.

- A senior police officer and the Director of Public Prosecutions DPP.L will have to issue a report saying more than 28 days is needed to obtain necessary evidence.

- The Home Secretary would then have to obtain independent legal advice on whether there was a grave, exceptional threat, that the extra powers were urgently needed and that the provision was compatible with the European Convention on Human Rights.

The Home Secretary would then sign an order immediately, allowing police to hold suspects for up to 42 days. Those powers would last for a maximum of 30 days.

- The order must be placed before parliament as soon as possible, along with a copy of the legal advice received. The powers would lapse after seven days unless both Houses of Parliament approve the measure.

- The Home Secretary must also notify the chairmen of the Home Affairs Select Committee, the Joint Committee on Human Rights and the Intelligence and Security Committee.

- Meanwhile each suspect's individual case will be subject to strict judicial oversight, with a judge's approval needed every seven days. A judge can only grant an extension if satisfied it is necessary and the investigation is being carried out "diligently and expeditiously".