The Spanish government defended on Wednesday its pick to helm the central bank - a minister in the Socialist-led administration - countering the opposition's protest that the appointment undermined the bank's independence.

"Jose Luis Escriva is one of the best economists this country has, he's one of the best experts on monetary policy," Prime Minister Pedro Sanchez said in a televised statement.

Economy Minister Carlos Cuerpo earlier confirmed the appointment of Escriva, the minister for digital transformation and civil service and a close ally of Sanchez, and told a parliamentary committee the bank's transparent structure shielded it from government interference.

He praised Escriva's background as the first chief of Spain's Independent Authority for Fiscal Responsibility, a budget stability watchdog he led from 2014 to 2020, when he became a minister, as well as head of the ECB's monetary policy division between 1999 and 2004.

But the conservative opposition People's Party said Sanchez was "colonising" institutions by packing them with loyalists.

"Only (dictator Francisco) Franco would have dared to name a minister as governor," said PP lawmaker Jaime de Olano, who also criticised Escriva's track record as a civil servant.

Meanwhile, Carlos Martin of the Socialists' hard-left junior coalition partner Sumar, described Escriva as a "suitable candidate", adding that ECB President Christine Lagarde and Vice President Luis de Guindos, a Spaniard, had held similar government posts before their current tenure.

Lagarde served as French trade minister under President Jacques Chirac and as agriculture and later finance minister during Nicolas Sarkozy's presidency. De Guindos was economy minister in the PP government of Prime Minister Mariano Rajoy.

A European banking supervision source told Reuters that Escriva could be seen as a non-independent appointee, since he helped draft the next budget and spearheaded a pensions reform, matters on which he would now have to have an unbiased view.

However, in neighbouring Portugal, former Finance Minister Mario Centeno, a Socialist, has run the central bank for the past four years without a hitch.