LONDON  - The Bank of England kept rates steady on Thursday but two of its policymakers unexpectedly voted for an immediate rate rise, in a statement that will boost investors' confidence that borrowing costs will rise in May.

Ian McCafferty and Michael Saunders - who were the first officials to call for rates to rise in 2017 - said it was now time for rates to increase again for only the second time since the 2008 financial crisis.

Globally, the economy is growing at its fastest rate since the 2007-2008 financial crisis, helping Britain's at a time when it is suffering from uncertainty about Brexit.

The United States Federal Reserve on Wednesday raised rates for the sixth time since the financial crisis. Even the European Central Bank - which is still struggling with anemic price growth - has its eye on phasing out its massive bond purchases.

The BoE's Monetary Policy Committee as a whole voted 7-2 to keep rates at 0.5 per cent but said "ongoing tightening" was likely to be needed to return inflation of 2.7 per cent back to target.

Last month BoE Governor Mark Carney and his colleagues surprised markets by saying rates might need to go up faster than expected, due to a strong global economy and an inflation rate that is running uncomfortably above target.

On Thursday, the BoE said that economic developments since then broadly backed up this view.

"Given the prospect of excess demand over the forecast period, an ongoing tightening of monetary policy over the forecast period would be appropriate to return inflation sustainably to its target at a more conventional horizon," the BoE said.

The BoE raised rates for the first time in over a decade in November, reversing an emergency cut made not long after Britain's June 2016 Brexit vote when the economy appeared to be cratering.

Since then, growth has proven better than expected - though last year the economy lagged a global upturn as high inflation caused by sterling weakness since the vote ate into households' disposable income.

No economist polled by Reuters expected the BoE to follow up on its rate hike in November - its first since 2007 - with a rate hike at its March meeting, and only a minority expected Saunders or McCafferty to vote for a rise.

One major stumbling block was removed this week when Prime Minister Theresa May agreed a transition deal with the European Union to leave trade relations between Britain and the bloc unchanged after Brexit in March next year until the end of 2020.

The BoE said this had given a boost to sterling.

Data on Wednesday that showed pay growth at its highest since 2015 also bolstered policymakers' certainty that domestic cost pressures were building, hampering inflation's return to target. Also on Wednesday, the government announced a 6.5 per cent pay rise for many public health workers over the next three years, breaking with seven years of pay restraint.

The growth picture in Britain is more muted. Last month the BoE forecast growth of 1.8 per cent this year and next - well below Britain's historic average - and last week government forecasts were gloomier, with Brexit exerting a drag on the outlook.

The BoE said snow in March was likely to cause first-quarter growth to slow to 0.3 per cent, but that this did not affect the medium-term outlook for growth.