Hammoudi puts the problem this way:

The central issue is that although these products allow banking to take place without offending Shari’ah compliance – haram conventional banking products sanitized to become halal … there is a certain level of expectation within the contemporary Muslim community that social justice, mutuality, and fairness are supposed to be centerpieces’ of Islamic banking institutions, but ‘that expectation is not being met by the current means of approaching Islamic finance’ … some of the products have been created through ‘artifice’; Constructing products that follow the letter of the law so that they are not illegal per se … The larger conventional banks and smaller Islamic banks operate in much the same way … both types of institutions attempt, more or less, to figure out ways to mimic interest rates without explicitly doing so … (Ibid.: 34-5) My assessment of Sukuk is that it is indeed one of the products, which appear to be Shari’ah- compliant and in accordance with the letter of the law, but which are not within the spirit of the law. Specifically, it has been manipulated to change it from a genuinely M(1) – M(2); M(2)>M(1) transac on by making it ‘asset-backed’ to become a M-C transaction and making it resemble equity-financing. As I understand it, since Shari’ah considers money to be a medium of exchange and not an asset in itself, it requires that one should not be able to receive money from money. The M(1) – M(2) transaction reflects the time value of money; which, as we have seen in earlier chapters, is not permissible.

Source: Prof. Iraj Toutounchian, Thoughts from Iraj Toutounchian’s Islamic Money & Banking: Narrated by Camille Paldi. Republished with permission.