Britain's economy grew less strongly than previously thought in much of 2015, according to official data that is likely to surprise the Bank of England as it ponders when to raise interest rates, Reuters reported.

Britain's economy grew by 0.4 percent in the third quarter, down from a previous estimate of 0.5 percent, the Office for National Statistics said on Wednesday.

Weaker growth in the country's huge services sector, especially in financial services, was behind the new, lower assessment of growth, the ONS said.

In annual terms, growth was revised down to 2.1 percent from a previous reading of 2.3 percent.

Economists taking part in a Reuters poll had expected no change to the previous ONS estimates.

The ONS also lowered its estimate of growth in the April-June period to 0.5 percent from 0.7 percent in quarterly terms and to 2.3 percent from 2.4 percent in annual terms.

The BoE has previously said it expects growth in the third quarter to come in at 0.6 percent.