The former head of MI5 has backed calls to legalise some drugs, saying drug policy should no longer be a "taboo subject".

Speaking at a meeting of the All Party Parliamentary Group on Drug Policy Reform, Baroness Eliza Manningham-Buller said countries like Portugal - where drugs have been decriminalised - could be an "example" to Britain.

"Should we follow Portugal's fascinating example and focus on drug use as a health issue rather than a crime issue?"

And Manningham-Buller said drug policy should be "at the forefront of national debate".

"Given its effects on us all and the enormous cost of our efforts to limit the problems which drugs cause, I find it extraordinary that it is not at the forefront of national debate. Instead there is a presumption that the current policy is the best we can do. And there is knee-jerk opposition to any change."

The comments came after Baroness Meacher, chair of the All Party Group on Drug Policy Reform, said on Thursday morning that countries which had decriminalised drugs such as the Czech Republic and Portugal had lower levels of problematic drug use.

"It is fairly clear that you do quite well if you have decriminalisation. That is one of the policies that we feel should be looked at.. It should be a cross-party commission in our view, because if you can take the politics out of this you can look at the evidence in a sensible way."

The group have said the government should review their drug policy and consider legalising some substances, as the war on drugs is not working.