* ECB Forum on Central Banking May 25-27 in Sintra, Portugal
* Billed to become ECB's version of Jackson Hole
* ECB President Draghi, IMF's Lagarde among speakers
* Meeting comes just before key ECB June policy meeting
FRANKFURT, May 23 (Reuters) - The European Central Bank launches its own version of the prestigious Jackson Hole annual retreat in Portugal on Sunday, inviting policymakers and academics to debate ahead of June's crunch policy meeting.
About 150 central bank governors, key government officials, academics and financial market representatives will gather from Sunday to Tuesday in a luxury resort in Sintra, northwest of Lisbon, once a summer retreat of the Portuguese aristocracy.
The conference is modelled along the U.S. Federal Reserve's annual monetary policy symposium in Jackson Hole, in Wyoming's Grand Teton National Park.
Themed 'Monetary Policy in a Changing Financial Landscape', the meeting comes less than two weeks before the ECB's June policy meeting, at which the central bank is expected to act to counter persistently low inflation.
This will be firmly on participants' minds even though officially the conference wants to be a forum to exchange research results and ideas.
"One big focus will be on what the ECB could possibly deliver in June, but I would imagine that they will be taking a longer term view as well," said Nick Matthews, senior European economist at Nomura.
ECB President Mario Draghi said after the May meeting that the Governing Council was "comfortable with acting next time" - its June 5 policy meeting - but wanted to see updated economic projections from the bank's staff first.
Since then data confirmed a slight increase in euro zone inflation in April to 0.7 percent from 0.5 the previous month, but also showed that the euro zone economy grew less than expected at the start of the year.
Five senior sources told Reuters last week the ECB was preparing a package of policy options, including cuts in all its interest rates and targeted measures aimed at boosting lending to small- and mid-sized firms.
ECB policymakers have come out in force to underline the central bank's readiness to act, with ECB Executive Board member Yves Mersch sending the strongest message yet by saying the likelihood that the Governing Council would already act at its next monetary policy meeting had grown substantially.
Calls from international organisations and the French government have grown louder over recent weeks, urging the central bank to add more stimulus and temper the strength of the euro.
On Sunday, Christine Lagarde, managing director of the International Monetary Fund and a vocal proponent of more active policy, kicks off the conference by talking about "monetary policy in the 'new normal"' in her dinner speech.
"Draghi will have a chance to respond to some of the points the IMF may raise the night before on Monday morning or to add anything to the message from the May meeting," Matthews said. "Although I think the message was loud and clear."
(Editing by Mike Peacock)