Unilever and City of London bankers have joined a growing chorus among the business community calling on Britain not to leave the European Union.
Paul Polman, chief executive of the international consumer goods giant, warned that Unilever could pull back its investments in Britain "kicked agains the table" and left the political bloc.
"We will always look at things," he said, when asked if Unilever, which employs 7,000 people in the UK, could reduce its presence in the country.
He said: "We are a positive contributor in that sense to the UK economy and we [would] have to look at that then for the UK versus Europe, just like we do in any other country that is not in the EU."
The Unilever boss said he backed reforming Britain's relationship with the EU but warned that the debate tended to ignore "all the good things that the common market has brought".
Polman made his remarks as Unilever, makers of PG Tips Tea, Dove shampoo and Magnum ice-cream, unveiled better than expected results for 2013, posting a £4.4 billion profit.
The Unilever boss' intervention comes after David Cameron promised to hold an in-out referendum on the UK's EU membership by 2017 after attempting to claw back powers.
Banks in the City of London said there was an "overwhelming case" for the government to deepen its ties with the European Union.
In a submission to a Treasury review of the powers held by London and Brussels, the British Bankers Association said: "Given the significance of financial services to the UK and the degree to which legislation is set at an EU level, there is an overwhelming case for the UK to devote further resource and expertise in engaging in the European process to increase the level of influence in priority areas."
Unilever and the BBA's intervention comes after the UK head of aerospace giant Airbus Group warned on Tuesday that Eurosceptics would need to offer a "compelling" alternative for how Britain could operate outside the EU without putting growth at risk.
Robin Southwell, president of Airbus Group's UK wing, said that the company, which employs 17,000 people in the UK, owed its success to Britain's continued membership of the European Union.
"Airbus Group... would never have achieved its success to date, without a working and effective partnership of countries and companies within Europe, which only collectively can deliver the scale required to be globally successful.
"Any other economic model which seeks or offers to change the dynamic and advantageous characteristics which we presently enjoy - and believe are optimal to our delivering sustained growth and employment - would need to specifically address this quite proper challenge in a detailed and compelling manner.”
Lib Dem MEP Graham Watson said: "Airbus Group is one of the most successful companies in Europe and has created thousands of highly skilled manufacturing jobs in this country.
"Key to its success has been the ability to trade freely in a single market of over 500 million.
“Liberal Democrats, as the party of In, are determined to defend Britain’s membership of the EU and the massive economic benefits that it brings.
"We cannot let the eurosceptics win the argument and throw our economic recovery away."