Web Summit has confirmed that it has signed a deal with the Portuguese government that will keep the event in Lisbon until 2028.

The €110m agreement will see the size of the venue double in size by 2022 to accommodate the summit's rapid expansion.

The contract also includes a €3 billion buyout clause that would require another city to compensate Lisbon if it were to buy the rights to host the conference during the decade-long period.

This is based on an estimate by the Portuguese government that Web Summit is worth over €300m to the country per year.

The announcement was made by co-founder and CEO of Web Summit, Paddy Cosgrave, along with the Prime Minister of Portugal, Antonio Costa and Lisbon's Mayor, Fernando Medina, in the city this morning.

"We're incredibly excited to be staying in Portugal," Mr Cosgrave said in a statement.

"Without a larger venue this would not be possible. Even until a few months ago, we never believed it would be possible. The plans are incredible and we're very thankful to all those who have worked on them," he added. 

The deal follows a competitive tender process that began over a year ago, during which more than 20 cities across Europe submitted bids to host the event.

Among those competing were Berlin, Paris, London, Madrid, Milan and Valencia.

The existing venue will have its capacity more than doubled as part of the deal between now and 2022.

Work will begin on the initial phase in the next few months and is scheduled to be complete in time for next year's event.

It will be followed by two further phases of growth.

More than 60,000 people are expected to attend the event this year, with attendees from 170 countries.

In 2016 Web Summit moved from Ireland to Lisbon for an initial period of three years.

Founded in Dublin in 2010 as a technology-focused conference, it has rapidly grown into one of the world's largest conference events of its kind and now includes a variety of subject areas in its programme.

It also runs events in Asia and the United States, and this year held its smaller MoneyConf fintech event in Dublin.