'Brexit' would lop 4 pct pts off UK GDP growth, hit pound 15-20 pct - Citi

LONDON, Feb 5 (Reuters) - Economic growth in Britain would be up to 4 percentage points lower over the next four years and sterling could lose a fifth of its value if the country votes to leave the European Union, economists at U.S (Other OTC: UBGXF - news) . bank Citi said on Friday.

Citi is the latest big bank to say that so-called 'Brexit' would take a "significant" toll on the UK economy, hitting sterling and sending inflation sharply higher.

"Brexit would probably trigger major economic weakness and a political crisis in the UK ... with a 15-20 percent depreciation of sterling in trade-weighted terms, resultant return to import-driven inflation and a major policy dilemma (for the Bank of England," Citi's team, led by Michael Saunders, wrote in a note.

A Brexit scenario we would trim 1-1.5 percentage points off Citi's gross domestic product growth forecasts for 2017, 2018 and 2019, or a total GDP loss of around 4 percent, they wrote.

Leaving the EU would hit exports, investment and consumer spending, while workforce growth would slow because Brexit would lead to a drop in inward migration, either because of legal barriers or because of Britain's "reduced attractiveness," they said.

The 15-20 percent fall in sterling would lift inflation, which has been virtually zero for the past year, up to 3-4 percent for several years, they added. Sterling is currently worth around $1.45 and the euro around 77 pence .

Earlier this week, U.S. bank Goldman Sachs (NYSE: GS-PB - news) also said the pound could lose up to 20 percent in the event of a vote for Brexit.

Prime Minister David Cameron has promised to hold a referendum before the end of 2017 but a date this summer is increasingly expected. (Reporting by Jamie McGeever; Editing by Mike Dolan and Hugh Lawson (Other OTC: LWSOF - news) )