ECB policymaker hints fuel QE fire

A slew of comments by European Central Bank (ECB) policymakers this week have further fueled expectations that a full-blown European quantitative easing (QE) program is a question of "when?" rather than "if?"

Recent figures confirmed that the euro zone has slipped into deflation, spurring a number of analysts and economists to argue that government bond-buying to stimulate the economy could be announced at the ECB's next meeting on January 22.

As such, market watchers have been speculating over what form such stimulus could take, with a source telling CNBC on Monday that QE could be based on the paid-in capital contributions made from national central banks to the ECB.

Read MoreECB plans QE according to paid-in capital: Source

Meanwhile on Friday, Reuters reported that the bank was considering a hybrid approach to government bond purchases, which would combine the ECB buying debt and separate purchases by national central banks.

The ECB's headquarters in Frankfurt
Thomas Lohnes | Getty Images News | Getty Images
The ECB's headquarters in Frankfurt

As the rumor mill over ECB QE goes into overdrive, the central bank's own policymakers have spoken out ahead of the meeting next week. Here is what they've been saying:

Sooner rather than later: ECB's Nowotny

Ewald Nowotny, a member of the ECB's Governing Council, said on Monday that the central bank needed to act sooner rather than later in order to spur growth and inflation, Reuters reported.

"You always have to consider that monetary policy has an impact only after a long delay," he said at a panel discussion organized by news outlet nzz.at. "That means if I want to do something I should do it sooner rather than later."

Nowotny added that steps, including bond buying, were still being discussed.

Last Friday, a source told CNBC that the central bank had discussed a 500-billion-euro ($593 billion) QE program, but Nowotny stressed: "We have a lot of things in motion and I think it would not be right to go into great detail now."

QE needs a limit: ECB's Noyer

Meanwhile, another high-profile member of the ECB's Governing Council said on Monday that there needed to be a cap on any purchases of government bonds.

Speaking to German newspaper Handelsblatt, Christian Noyer added that although nothing had been decided yet, the debate was, "not only about whether we should do it at all - but also about when we should do it."

"My personal reading is that if we were to decide to have a government bond-buying program, we should have a cap in terms of the percentage of what we would be buying," Noyer said in the interview. "So that most of the financing will continue to rely on the private market."

ECB Ready For QE If Needed: ECB's Makuch

Governing Council member Jozef Makuch, meanwhile, said that the ECB was is ready to launch quantitative easing if needed, but stressed that it was too early to say what exactly this policy would consist of.

Speaking to Slovak news agency TASR on Monday, Makuch was quoted by Reuters as saying that it was, "too early to say what that would entail, because the programme has not been brought into life yet."

"The ECB is ready for further steps. From credit easing, or measures to support lending, if they are not successful, we have to move to quantitative easing," Makuch told TASR.

A stumbling block?

One potential issue that could put prove problematic for the ECB is a decision by the European Court of Justice in Luxembourg, due on Wednesday.

The court is expected to respond to a legal challenge to the ECB's Outright Monetary Transactions (OMT) – an as-yet unused bond-purchase program seen as a precursor to QE.

Germany's Constitutional Court opposed OMT, arguing that it would mean that the ECB was acting outside its remit. Although non-binding, the European court's decision will be seen as a green – or red – light on QE.

- By CNBC's Holly Ellyatt, follow her on Twitter @HollyEllyatt. Follow us on Twitter: @CNBCWorld