A row has broken out over methadone programmes and the effectiveness of residential rehabilitation for drug addicts.

It came after details emerged of occupancy rates in some centres of below 50% at a time when drug deaths are rising.

It has been reported that Beechwood House in Inverness has only 40% occupancy while Phoenix Futures in Glasgow is only half full. Drugs charity the Scottish Recovery Consortium wants a summit to try to find out why the rates are so low.

The head of Stirling University's Scottish Addiction Studies group Rowdy Yates told BBC TV's Sunday Politics that the residential sector was on the wane.

Dr Richard Watson, of the Royal College of General Practitioners, stated his opposition to residential rehabilitation and gave his backing to methadone treatment, despite its being linked to 47% of Scottish drug deaths in official statistics for 2011 published in August.

He said: "Methadone decreases the death rate in those who are prescribed it at least five or six fold, it decreases illegal drug use, it decreases crime."

The Scottish Government is reviewing its methadone scheme and MSPs will debate drugs strategy this week.