"I confirm that we have a policy to accept collateral ... at a rating threshold of single-A," Trichet told a news conference here.
"That's what we've been doing since the launch of the euro in 1999. Since 1999 we had never taken collaterals below this rating threshold."
Asked to specify what the threshold was, he said "All (that) is A", meaning anything from A-minus ("A-") upwards.
Trichet was responding to questions following a newspaper report that said the guardian of the euro planned to snub the sovereign debt of countries repeatedly breaching the EU's budget rules as a way of imposing fiscal discipline.
The Financial Times said the ECB planned to step up pressure on such countries that consistently flout the EU's budget rules by refusing to accept their sovereign debt as collateral if their credit ratings slipped too far.
Quoting "EU financial policy-makers", the newspaper said the ECB would make clear in future that it would accept only bonds with at least a single A-minus ("A-") rating from one or more of the main rating agencies as collateral in its financial market activities.
The move would act as a warning to over-spending governments, since a refusal by the ECB to accept a government's bonds would make those bonds harder to sell, the FT said.
Such a snub would be a humiliating swipe at the over-spending countries and would drive up the interest rate paid by a government to finance its debt.
The newspaper quoted EU government officials as saying that the ECB had discussed its collateral strategy with eurozone finance ministers and a formal confirmation could be expected soon.
Trichet said Wednesday that the FT report showed there was need for clarification on the ECB's policy, which had not changed since 1999.
And he insisted that the bank made no differentiation between public and private sector debt. "We treat the private sector and the public sector in the same fashion," he said. To finance their day-to-day business, commercial banks borrow from the central bank, using bonds, mostly government debt, as collateral.
The ECB is currently coming under increasing political pressure to hold off raising its key interest rate for the time being, for fear of stifling the still fragile economic recovery in the euro area. Luxembourg premier and Eurogroup chief Jean-Claude Juncker urged the bank this week "not to take an inconsiderate monetary (policy) decision", comments that are likely to have irritated the ECB, which is notoriously touchy if it feels politicians are trying to meddle in its monetary policy decisions.
"You will have noted that I said nothing after the meetings with the Eurogroup," Trichet said.
The ECB regularly invites politicians and European officials to its regular policy-setting meetings and the bank never has divulged what was said at those meetings, the Frenchman said. Asked whether he expected additional political pressure on rates, Trichet retorted: "I expect absolutely nothing." But he reinforced the message he sent to the markets last week when he said the ECB was ready to act "at any time" to raise eurozone borrowing costs to curb inflation.