The European Central Bank has warned banks across the euro zone to curb payouts to shareholders.

It has also pledged to probe how much they are paying in bonuses as the rest of the bloc's economy suffers. 

In its boldest public order to the industry since health checks last year uncovered problems mainly in Italy, the ECB said banks should be setting aside more money for rainy days ahead. 

"Banks should base their dividend policies on conservative and prudent assumptions,  so that after any pay-out they can still fully cover their current capital requirements and prepare themselves to meet more demanding capital standards", Daniele Nouy, the ECB's supervisory chief said.

The demand is legally enforceable on banks that failed the tests, such as Italy's Monte dei Paschi, provided they are still short of capital. 

Other lenders that the ECB would like to see top up their capital cushion, but who already meet the minimum threshold, may be able to legally avoid any clampdown on shareholder payouts. 

However, they will face considerable pressure from Frankfurt to fall into line. 

In a statement, the ECB urged banks to take the 'current challenging economic and financial conditions' into account when paying dividends. 

Late last year, the ECB conducted health checks, finding the biggest problems in Italy, Cyprus and Greece but also concluded that banks' capital holes had since chiefly been plugged. 

Referring in its statement to the payment of bonuses, the ECB said that it had told banks that "variable remuneration will be thoroughly reviewed in the coming months".