LONDON: Whether it is Brexit nerves or just a bad run on shaky financial markets, sterling is on course for its first April loss in 12 years, boding ill for the run-in to the referendum on EU membership in June.

While the pound has proved more robust since a collapse at the end of February, and it rose again on Monday, it is down just over 1 percent on the Bank of England’s trade-weighted measure of its strength so far this month.

That compares with a consistent run of strong performances in the first month of the UK financial year that stretches back more than a decade through the worst banking storms since the 1930s.

Traders and analysts have blamed the pound’s weakness on nerves ahead of the June 23 referendum on European Union membership, poorer expectations for global growth or a current account deficit that ballooned to 7 percent of economic output at the end of 2015.

“Even through the financial crisis and the run-up to the May 2015 General Election, sterling has consistently appreciated against the dollar during April,” said Kamal Sharma, an FX strategist with Bank of America Merrill Lynch in London.

“A combination of the end of the UK tax year and a heavy month of dividend payments by UK corporates are factors.”

Analysts say that either suggests sterling may have the potential to recover before the end of the month from current multi-year lows. Or it could signal worse is to come in May and June, once the support for sterling that normally shows up in April evaporates.

The market’s most-watched positioning data, from the US Commodity Futures Trading Commission, on Friday showed investors added to bets against sterling in the first week of this month.

But senior figures on banks’ FX sales desks warn that few institutional investors have as yet hedged against the risk of a Brexit, as leaving the EU is known.

A Reuters poll on Friday suggested the pound would fall 7 percent in the immediate aftermath of a vote to leave. Some banks say it could be closer to 20 percent.

Opinion polls suggest the vote is too close to call, though bookmakers’ odds tend to favor Britain staying in. “One thing that is clear is that institutional money is not prepared,” said the head of institutional currency sales at one of the top six FX trading banks by volume.

“At some point they are going to have to take a decision and we may see a real impact on sterling at that point.”