"This process of closing of proposals to acquire the debt ends tomorrow and on the same day the capital injection from the state", Centeno told journalists after an event in London organised by financial information company Bloomberg.

According to the minister, "Caixa will become a strong bank with levels of capital similar to those of the best European banks." That, he argued, "is very important for the Portuguese financial system, certainly for Caixa and for the confidence that there must be in the national banking system," which had "shown a lot of resilience during the [global financial] crisis" but suffered from insufficient capital.

The capacity of CGD and other Portuguese banks to attract interest from foreign investors represents an "enormous success", he said.

Since the collapse in 2014 of Banco Espírito Santo, then Portugal's largest non-state bank, all the country's major financial institutions other than CGD are controlled by foreign investors or are due to be sold to them.

CGD is currently seeking to bolster its balance sheet by a total €5 billion, in a lengthy process approved by the European Commission as not infringing European Union competition rules. Last year the bank had a record net loss of €1.859 billion.

So far it has booked €1.445 billion thanks to the transfer to the state of shares in ParCaixa and contingent capital instruments (also known as CoCos), and issued €500 million in perpetual debt. A further €430 million of the latter is to be issued over the coming 18 months.

The next phase of the process is a capital increase, with the state taking up €2.5 billion in new CGD shares.