Six funds have been awarded AAA ratings by Standard & Poor's in its latest review of high-income fund sectors.
Threadneedle's UK corporate bond, Aberdeen's sterling bond income and Schroders' international selection emerging market debt fund were all upgraded from AA status.
The Invesco GT gilt, Hend-erson horizon sterling bond and Henderson preference & bond funds all kept their top ratings.
The best-performing high-income sectors over the past 12 months were dollar global emerging debt and dollar global high yield, with median returns of 19.6 and 10.8 per cent respectively.
Fixed interest and gilt funds also held up well compared with equities, with median returns of 6.6 per cent and 4.6 per cent. Most equity funds are still registering negative returns for the past year.
Only four funds received rating downgrades from S&P. M&G high-yield corporate bond, Newton high-yield bond and Obliflex E pound sterling funds were downgraded from AA to A status while the Barclays sterling bond fund was reduced from AAA to AA.
S&P European director of research James Tew says: “One factor evident from this year's review has been the importance of a flexible investment mandate backed up by a pragmatic approach to challenging market conditions.
“Time and again our analysts have highlighted adaptability to market conditions, the flexibility in the choice of investment sectors and the scope to move away from benchmark weightings as ingredients for outperformance.”