The value of the currency has dipped from a four-month high to $1.5060 against the US dollar, Reuters reports, after the Bank stated that it is to inject a further £50 billion into the asset purchasing initiative.
Some investors have been surprised by the move, as they were not expecting the further funding to be used so soon.
Market strategist Joshua Raymond noted that the Bank is "trying to be aggressive" with its moves to stimulate the economy.
"There was largely no reaction from equity markets but sterling immediately fell," he remarked, adding that there is still £25 billion in reserve that the Bank may use in future months.
Sterling is the second currency to decline in trading today, with the euro falling this morning amid concerns that the European Central Bank may adopt similar quantitative easing tactics.