NatWest's sneaky catch to its latest ISA

Tim Ireland/PA Archive/Press Association Images

NatWest has just launched a new cash ISA offering up to 4.2% in fixed interest, which is virtually unheard of in the current market, and immediately thrust it to the top of the best-buy tables.

However, a report by Thisismoney is warning savers that it comes with a hefty catch - and one which renders the account far less competitive.