"Some reservations" were expressed about the "precise timing and proposed scale" of the European Central Bank's expansion of its Pandemic Emergency Purchase Programme, according to minutes of its 3-4 June meeting.

The details, published today, mark the first time the ECB has published an extensive account of one of its meetings.

The minutes do not mention who expressed reservations about the programme's expansion, however. 

It notes and goes into some detail behind the proposal, subsequently "broadly agreed", to expand the bond-buying programme by €600 billion and to extend it into June of next year.

It says the ECB's chief economist, Philip Lane, presented the proposal and outlined "an unprecedented contraction of the euro area economy", which has led to a downward revision in the projected level of economic activity and inflation outlook. 

The account said that members "generally" agreed with the assessment. 

However, the account also describes how some members identified "some indications of a bottoming-out" and were "seen to argue for a more cautious approach."

Ultimately it was agreed that bond buys are the best tool in the circumstances and their benefits outweigh costs.

Seen as an indirect response to the a challenge by Germany's Constitutional Court, the ECB defended the asset buys.

It argued that ample evidence has been amassed to prove that buying government bonds was the best way to revive the euro zone economy and prop up inflation. 

Germany's Constitutional Court ruled last month that the ECB overstepped its mandate with over €2 trillion of government bond purchases.

It ordered the Bundesbank to quit the scheme unless the ECB can prove proportionality within three months. 

"There was now ample evidence from an exhaustive literature showing that asset purchase programmes in general and the Public Sector Purchase Programme in particular had proven effective in achieving their intended effects on the euro area economy and thereby in maintaining price stability," the ECB said in the accounts of the meeting. 

Policymakers agreed this week to give vital documents to German authorities to prove proportionality but the ECB will not directly engage in the process, leaving the Bundesbank to spearhead the process. 

In parallel, the ECB has been drawing up contingency plans to carry out its multi-trillion bond-buying programme without the Bundesbank and launch an unprecedented legal action against the German central bank. 

Facing the biggest economic contraction in generations, policymakers at the June meeting extended emergency bond purchases until mid-2021 and increased them by €600 billion to €1.35 trillion to help governments finance their crisis response. 

Additional reporting Reuters