LONDON (Reuters) - Net migration of European Union citizens into Britain almost halved in the 12 months to September, according to data that alarmed business groups who say Brexit is leaving companies without enough candidates to fill jobs.

Official data on Thursday showed a net 244,000 people of all nationalities moved to Britain during the period, down 29,000 from the same point in 2016, official data showed on Thursday.

While net migration to Britain from non-EU countries hit an almost six-year high, for EU citizens the number fell to 90,000 from 165,000 in the 12 months to September, the Office for National Statistics (ONS) said.

Overall, the figures added to signs that the June 2016 decision by voters to leave the EU has had a big impact on people moving to and from Britain.

Lowering immigration was a big reason many Britons voted to leave the EU, but industry groups said businesses were suffering.

“To compete, the UK needs to be somewhere that people want to come to work, and regrettably, increasingly it isn’t,” said Neil Carberry, managing director for people and infrastructure at the Confederation of British Industry.

The Institute of Directors said the figures compounded businesses’ concern about access to labor while the EEF, a manufacturers’ association, said Britain needed to assure EU citizens they were needed and welcome.

On Wednesday, Prime Minister Theresa May said she wanted all EU citizens living lawfully in Britain to stay after Brexit in 2019 and she promised a smooth registration system.

Pro-Brexit campaigners said Thursday’s figures showed immigration remained too high and that the net migration figure was as large as the population of some major British cities.

Separately, recruiter Hays said construction sites were seeing labor shortages as Eastern Europeans, who typically fill most positions, were looking elsewhere.

Other sectors, like nursing, have also reported shortages that have intensified since the Brexit vote.

COMINGS AND GOINGS

The number of EU citizens moving to Britain stood at 220,000 in the 12 months to September, the smallest inflow in more than three years. By contrast, 130,000 EU citizens left Britain -- the biggest outflow since the year to December 2008, during the financial crisis.

The number of EU citizens moving to Britain for work dropped to the lowest in more than four years -- chiming with data on Wednesday that showed the number of EU workers in Britain rising in 2017 at the slowest annual rate since mid-2013.

The ONS said the rise in non-EU net migration mostly reflected more people coming to Britain to study. The increase was flattered by an unusual dip in the same period a year ago.

May has been urged to exclude students from migration statistics. Critics say the government has exaggerated the risk that students stay in Britain after their visas expire.