Brexit will have resulted in 300,000 fewer UK holidaymakers visiting Ireland in 2018, compared with the previous 12 months, it has been warned.
Tourism body Failte Ireland said this could have resulted in €88m in lost revenue and 1,900 lost tourism jobs had there not been a strong performance in other markets, particularly the US.
There were 3.6 million UK visitors in 2017, but Failte Ireland is predicting 300,000 fewer next year.
The authority is to target cross-border holidaymakers in a bid to off-set the anticipated impact of Brexit on the industry.
Failte Ireland said it intends to significantly increase spending in the Northern Ireland market place in early 2018 in an attempt to encourage travel to the Republic of Ireland, particularly key border counties, in the off-season.
Research is also being conducted on the development of luxury breaks, outdoor adventure activities and the retention of golf tourism, which is worth about €100m annually to the Irish economy from the UK and North American markets.
Failte Ireland CEO Paul Kelly said the "volatility generated by Brexit during the last year would have led to significant revenue and job losses had other traditional markets, particularly the US, not performed so well."
He warned: "We cannot always assume that other markets will continue to compensate in this fashion - particularly as we now face a challenge in those markets from a British tourism product made much more competitive by the lower sterling value."
Mr Kelly said the ongoing Brexit volatility underlines "the extent to which tourism can be at the mercy of external factors beyond our control."
He added: "However, we can meet our current challenges by working on those things which remain within our control - our visitor experiences, competitiveness, capacity and skills."
He was speaking at the launch of Failte Ireland's Get Brexit Ready support programme designed to help businesses at risk or already struggling with the loss of trade created by Brexit.
The website is a one-stop shop for all the relevant information and insights that businesses will need - from development supports and training programmes to insights and market intelligence.
Tourism and sports minister Brendan Griffin welcomed the programme and warned that tourism businesses will need to diversify and reposition if they are to adapt to the evolving trading climate.
"The tourism environment has changed. We have less British visitors coming to Ireland and to compound that Britain has become more attractive as a destination for visitors that Ireland is also competing for," he added.
Details of the Get Brexit Ready programme can be found at www.failteireland.ie
Ireland's tourism and hospitality industry employs an estimated 220,000 people and generates an estimated €5.7bn in revenue a year.