These assets caused investors to lose almost 2 per cent over the fourth quarter of 2008.
The news comes after Standard Life’s pension sterling fund revaluation in January focused the spotlight on cash funds and the assets these so-called safe havens are invested in.
Standard Life recently said it would compensate investors who lost out, after admitting its fund literature was unclear.
But Pru is adamant its documentation has always laid out exactly what its funds have invested in. A spokesman says: “There is little similarity between Standard Life’s fund and ours. We have always been explicit about the holdings and the composition of the fund. We have always been clear that they are money market funds and can rise and fall.
“The mortgage-backed exposure is very limited and is highly concentrated in AAA, AA and A-rated issues and the fund hold upwards of two-thirds of its money in cash and deposits. The core rationale behind these funds remain sound.”