That would mark a 14 percent increase from where sterling is currently trading, at around $1.41, and would take it back to levels not seen since mid-2014.

The London-based bank said that political concerns surrounding the referendum on Britain's membership of Europe - due by 2017 but widely expected to come at some point this year - were weighing on sterling sooner than they had expected them to.

"The UK will need to get beyond 'Brexit' fears before sterling can strengthen, but once it does, the rally is set to be sizeable," the bank's currency strategists wrote in a research note.

The bank reckons strong domestic demand will force the Bank of England to raise interest rates much sooner than markets expect - investors are currently betting that rates will stay at their record lows until 2017. That should also boost the pound.

HSBC also revised up its forecast for the end of 2017, to $1.65 from $1.50 previously.

Against the euro, the bank raised its end-of-year forecast to 75 pence per euro and its end-2017 forecast to 73 pence. It had previously reckoned sterling would end both years at 80 pence per euro.

(Reporting By Jemima Kelly; Editing by Jamie McGeever)