A new team at Threadneedle Asset Management has won a mandate to oversee a $500m (€390m) portfolio of fixed income instruments largely backed by mortgages. However, views on the toxicity of the asset class remain as divided as the returns from various managers investing in the arena.

Securities based on residential and commercial loans have been shunned and sold short by many fund managers who have viewed them as largely a one-way bet, downwards, since at least the middle of last year, as defaults on US mortgages increased.