May 30 (Reuters) - Keir Starmer's decision to shine a spotlight on Nigel Farage's fiscal plans suggests it would be foolish to ignore the possibility of Farage succeeding Starmer as Britain's prime minister before the decade is out.

Starmer said on Thursday that Farage would crash Britain's economy if his Reform UK party ever won power, and said Farage's economic plan was similar to that of former Conservative Prime Minister Liz Truss.

Truss' economic plan famously torpedoed the pound in September 2022, when GBP/USD sank to a historic lower of 1.0327.

Reform's lead over Labour in opinion polls over recent weeks is the reason why Starmer has his sights trained on Farage, four years out from the expected next UK general election date.

Britain's first-past-the-post voting system means Reform has a chance of winning a Commons majority at the next election if it gets at least 30% of votes cast. Labour won a huge majority on a 34% vote share last July.

Cable is currently over 30 cents above its September 2022 nadir, having scaled a 39-month peak of 1.3593 at the start of this week.

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(Robert Howard is a Reuters market analyst. The views expressed are his own)