Almost half of UK business leaders are worried about post-Brexit skills shortages and fear they will not find enough suitable staff in 2017, according to a survey by one of the UK’s leading business organisations.

The polling by the Institute of Directors found overall levels of confidence higher than in the immediate aftermath of the Brexit vote, but nonetheless found four in 10 businesses worried about a lack of skills.

The findings, and comments by IoD leaders demanding an end to uncertainty over the future of EU citizens resident in this country, will add to pressure on Theresa May to bring forward a decision on the status of those citizens.

The IoD said its polling of business mangers demonstrated “the need for clarity on a long-term skills strategy and an immigration system that gives businesses access to the talented people they need”.

Asked which factors were having a negative impact on their companies, 44% of the 844 bosses questioned said uncertain trading relations with the EU in the aftermath of the Brexit vote was holding them back.

Half of them felt economic conditions in the UK in the aftermath of the vote were having a negative effect on their businesses, while 40% mentioned skills shortages.

Sentiment about the prospects for the economy post-Brexit vote had improved since the middle of the year, with more than 60% of IoD members voicing optimism about their own firms’ prospects in 2017. Expectations for the UK economy were also improved.

Simon Walker, the director general of the IoD, said businesses were “becoming used to uncertainty” but it was time for ministers to end doubts about the rights of more than 2.5 million EU citizens resident in this country.

“Business will now look to government to lay the groundwork for growth and, considering the skills shortage revealed in this survey, they should start by guaranteeing the status of EU citizens currently working for British businesses,” he said.

Last weekend the British Chambers of Commerce and TUC joined forces to make similar demands, fearing skills shortages for British businesses if EU residents left.

James Sproule, the IoD’s chief economist, said: “No doubt there are headwinds on the horizon, and if revenues are squeezed over the coming year then there will be consequences. Politicians must now look to build on this optimism with an ambitious pro-enterprise domestic agenda and a constructive start to our European negotiations.

“Confidence is a funny thing, and it can’t be taken for granted: a misjudged speech or signs that we aren’t making progress in Brussels could signal a sudden downturn. The budget in March remains a vital moment for this government and the economy as a whole. Encouraging firms to invest must remain top of the agenda.”