With regard to parts (a) and (b) of the question I refer the hon. Member to the website of the UN peacekeeping mission to Western Sahara (MINURSO):
This details factual information on the length of the berm, the materials it is made of and its history.
With regard to part (c) of the question, the UK regards the status of the disputed territory of Western Sahara as undetermined and continues to believe progress towards a negotiated solution to the dispute, providing for the self-determination of the people of Western Sahara, is best achieved under the auspices of the UN. Any issues relating to “the berm” will need to be resolved and considered in that context.
With regard to part (d) of the question we continue to believe that greater openness and transparency on human rights by all the parties to the dispute would create a significantly better environment for political dialogue. Both sides have imperfect records on human rights. Morocco's record in Western Sahara has improved in recent years, but more needs to be done to provide equality of opportunity for the people of the territory. We welcome the efforts of the parties, in partnership with MINURSO and NGOs, to reduce the threat posed by mines and unexploded ordnance in the region of the berm. We also support the UN Secretary-General's Personal Envoy to Western Sahara, Christopher Ross, in his efforts to build confidence between the parties, including encouragement to cooperate with the UN High Commissioner for Refugees towards establishing family visits by land.